Solid-state imaging device, method for manufacturing the same, and imaging apparatus

ABSTRACT

Realization of an adequate hole accumulation layer and reduction in dark current are allowed to become mutually compatible. A solid-state imaging device  1  having a light-receiving portion  12  to photoelectrically convert incident light is characterized by including a film  21 , which is disposed on a light-receiving surface  12   s  of the above-described light-receiving portion  12  and which lowers an interface state, and a film  22 , which is disposed on the above-described film  21  to lower the interface state and which has a negative fixed charge, wherein a hole accumulation layer  23  is disposed on the light-receiving surface  12   s  side of the light-receiving portion  12.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/598,691, filed Feb. 11, 2010, which is a national stage ofInternational Patent Application Serial No. PCT/JP2007/066116, filedAug. 20, 2007, which claims priority to Japanese Patent ApplicationSerial No. JP 2007-122370, filed May 7, 2007, the entire disclosures ofwhich are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a solid-state imaging device in whichan occurrence of dark current is suppressed, a method for manufacturingthe same, and an imaging apparatus.

BACKGROUND ART

Solid-state imaging devices formed from a CCD (Charge Coupled Device)and a CMOS image sensor have been previously widely used in videocameras, digital steel cameras, and the like. Noise reduction, as wellas sensitivity improvement, is an important issue common to thesesolid-state imaging devices.

In particular, a dark current, wherein electric charges (electrons)generated from fine defects present at a substrate interface of alight-receiving surface are taken in as signals so as to serve as amicro-current and be detected in spite of the fact that there is noincident light and, therefore, there is no pure signal charge generatedthrough photoelectric conversion of the incident light or a darkcurrent, a source of which is an interface state at an interface betweena light-receiving portion and an upper layer film, is a noise to bereduced with respect to a solid-state imaging device.

As for a technique to suppress generation of a dark current resultingfrom the interface state, for example, a buried photodiode structurehaving a hole accumulation (hole accumulation) layer 23 formed from a P⁺layer on a light-receiving portion (for example, photodiode) 12, asshown in FIG. 38 (2), is used. In this regard, in the presentspecification, the above-described buried photodiode structure isreferred to as an HAD (Hole Accumulated Diode) structure. As shown inFIG. 38 (1), regarding a structure including no HAD structure, electronswhich are generated on the basis of the interface state and which serveas a dark current flow into the photodiode. On the other hand, as shownin FIG. 38 (2), regarding the HAD structure, generation of electronsfrom the interface is suppressed by the hole accumulation layer 23formed at the interface. Furthermore, even when electric charges(electrons) resulting from the interface are generated, the electriccharges flow in the hole accumulation layer 23 of the P′ layer, in whichmany holes are present, and can be extinguished without flowing into acharge accumulation portion, which is a N′ layer in a light-receivingportion 12 and which serves as a potential well. Consequently, it can beprevented that the electric charges resulting from the interface serveas a dark current and are detected and, thereby, a dark currentresulting from the interface state can be suppressed.

As for a method for producing this HAD structure, in general, animpurity, e.g., boron (B) or boron difluoride (BF₂), which forms a P⁺layer, is ion-implanted through a thermal oxide film or a CVD oxide filmdisposed on a substrate and, thereafter, the implanted impurity isactivated through annealing so as to produce a P-type region in thevicinity of the interface. However, a heat treatment at a hightemperature of 700° C. or higher is indispensable to activate the dopingimpurity and, therefore, it is difficult to form a hole accumulationlayer through ion implantation by a low-temperature process at 400° C.or lower. Moreover, in the case where it is desired to avoid activationat high temperatures for a long period in order to suppress diffusion ofdopants, a method for forming a hole accumulation layer, wherein ionimplantation and annealing are conducted, is not preferable.

In addition, if silicon oxide or silicon nitride disposed as an upperlayer of the light-receiving portion is formed by a technique oflow-temperature plasma CVD or the like, the interface state deterioratesas compared with the interface between a film formed at hightemperatures and a light-receiving surface. This deterioration ininterface state causes an increase in dark current.

As described above, in the case where it is desirable to avoid the ionimplantation and the annealing treatment at high temperatures, it is notpossible to form the hole accumulation layer through ion implantation inthe related art, and the dark current tends to further deteriorate. Inorder to solve it, the need for forming the hole accumulation layer byanother technique not employing ion implantation in the related artarises.

For example, a technology has been disclosed, wherein charged particleshaving the same polarity as the conduction type opposite to theconduction type of a semiconductor region are embedded into aninsulating film, which is formed from silicon oxide, on a photoelectricconversion element, which is disposed in a semiconductor region andwhich has the opposite conduction type, so as to increase the potentialof a surface of the photoelectric conversion portion, and an inversionlayer is formed on the surface so as to prevent depletion in the surfaceand reduce generation of the dark current (refer to, for example,Japanese Unexamined Patent Application Publication No. 1-256168). In theabove-described technology, a technology to embed charged particles intothe insulating layer is needed. However, it is not clear what embeddingtechnology is employed. Furthermore, electrodes are needed for chargeinjection in order to inject the electric charge from the outside intothe insulating layer, as is employed in non-volatile memory in general.Even if the electric charge can be injected from the outside in anon-contact manner without employing an electrode, it is necessary thatthe electric charge trapped in the insulating film is not detrapped, sothat a charge retention characteristic becomes a problem in any event.For that purpose, an insulating film having a high charge retentioncharacteristic and high quality has been demanded, but realization hasbeen difficult.

A problem to be solved is that in the case where formation of anadequate hole accumulation layer through high concentration ionimplantation into a light-receiving portion (photoelectric conversionportion) is intended, since the light-receiving portion is damagedbecause of the ion implantation, an annealing treatment at hightemperatures is indispensable and, at that time, diffusion of impuritiesoccurs and the photoelectric conversion characteristic deteriorates. Onthe other hand, in the case where the ion implantation is conducted at alow concentration in order to reduce the damage due to the ionimplantation, a problem is that the concentration of the holeaccumulation layer is reduced and a function as a hole accumulationlayer is not adequately provided. That is, the problem is that it isdifficult to allow realization of an adequate hole accumulation layerand reduction in dark current to become mutually compatible whilediffusion of impurities is suppressed and a desired photoelectricconversion characteristic is provided.

It is an object of the present invention to allow realization of anadequate hole accumulation layer and reduction in dark current to becomemutually compatible.

DISCLOSURE OF INVENTION

A solid-state imaging device (first solid-state imaging device)according to the present invention is characterized in that thesolid-state imaging device having a light-receiving portion tophotoelectrically convert incident light includes a film, which isdisposed on a light-receiving surface of the above-describedlight-receiving portion and which lowers an interface state, and a film,which is disposed on the above-described film to lower the interfacestate and which has a negative fixed charge, wherein a hole accumulationlayer is disposed on the light-receiving surface side of theabove-described light-receiving portion.

In the above-described first solid-state imaging device, since the film,which has a negative fixed charge, is disposed on the film, which lowersthe interface state, the hole accumulation (hole accumulation) layer isformed adequately at the interface on the light-receiving surface sideof the light-receiving portion by an electric field resulting from thenegative fixed charge. Therefore, generation of electric charges(electrons) from the interface is suppressed and, in addition, even whenelectric charges (electrons) are generated, the electric charges do notflow into a charge storage portion serving as a potential well in thelight-receiving portion, flow through the hole accumulation layer, inwhich many holes are present, and can be extinguished. Consequently, itcan be prevented that the electric charges resulting from the interfaceserve as a dark current and are detected by the light-receiving portion,and a dark current resulting from the interface state can be suppressed.Furthermore, since the film, which lowers the interface state, isdisposed on the light-receiving surface of the light-receiving portion,generation of electrons resulting from the interface state is furthersuppressed, so that flowing of electrons, which serve as a dark current,resulting from the interface state into the light-receiving portion issuppressed.

A solid-state imaging device (second solid-state imaging device)according to the present invention is characterized in that thesolid-state imaging device having a light-receiving portion tophotoelectrically convert incident light includes an insulating film,which is disposed on a light-receiving surface of the above-describedlight-receiving portion and which transmits the above-described incidentlight, and a film, which is disposed on the above-described insulatingfilm and which applies a negative voltage, wherein a hole accumulationlayer is disposed on the light-receiving surface side of theabove-described light-receiving portion.

In the above-described second solid-state imaging device, since thefilm, which applies a negative voltage, is disposed on the insulatingfilm disposed on the light-receiving surface of the light-receivingportion, the hole accumulation (hole accumulation) layer is formedadequately at the interface on the light-receiving surface side of thelight-receiving portion by an electric field generated throughapplication of a negative voltage to the film, which applies a negativevoltage. Therefore, generation of electric charges (electrons) from theinterface is suppressed and, in addition, even when electric charges(electrons) are generated, the electric charges do not flow into acharge storage portion serving as a potential well in thelight-receiving portion, flow through the hole accumulation layer, inwhich many holes are present, and can be extinguished. Consequently, itcan be prevented that the electric charges resulting from the interfaceserve as a dark current and are detected by the light-receiving portionand a dark current resulting from the interface state can be suppressed.

A solid-state imaging device (third solid-state imaging device)according to the present invention is characterized in that thesolid-state imaging device having a light-receiving portion tophotoelectrically convert incident light includes an insulating film,which is disposed as an upper layer on the light-receiving surface sideof the above-described light-receiving portion, and a film, which isdisposed on the above-described insulating film and which has a value ofwork function larger than that of the interface on the light-receivingsurface side of the above-described light-receiving portion to conductphotoelectric conversion.

In the above-described third solid-state imaging device, since the film,which has a value of work function larger than that of the interface onthe light-receiving surface side of the light-receiving portion toconduct photoelectric conversion, is included on the insulating filmdisposed on the light-receiving portion, holes can be accumulated at theinterface on the light-receiving surface side of the light-receivingportion. Consequently, a dark current is reduced.

A method for manufacturing a solid-state imaging device (firstmanufacturing method) according to the present invention ischaracterized in that the method for manufacturing a solid-state imagingdevice having a light-receiving portion, which photoelectricallyconverts incident light and which is disposed on a semiconductorsubstrate, includes the steps of forming a film, which lowers aninterface state, on the above-described semiconductor substrate providedwith the above-described light-receiving portion and forming a film,which has a negative fixed charge, on the above-described film, whichlowers the interface state, wherein a hole accumulation layer is formedon the light-receiving surface side of the above-describedlight-receiving portion by the above-described film, which has anegative fixed charge.

In the above-described method for manufacturing a solid-state imagingdevice (first manufacturing method), since the film, which has anegative fixed charge, is disposed on the film, which lowers theinterface state, the hole accumulation (hole accumulation) layer isformed adequately at the interface on the light-receiving surface sideof the light-receiving portion by an electric field resulting from thenegative fixed charge. Therefore, generation of electric charges(electrons) from the interface is suppressed and, in addition, even whenelectric charges (electrons) are generated, the electric charges do notflow into a charge storage portion serving as a potential well in thelight-receiving portion, flow through the hole accumulation layer, inwhich many holes are present, and can be extinguished. Consequently, itcan be prevented that a dark current due to the electric chargesresulting from the interface is detected by the light-receiving portionand a dark current resulting from the interface state can be suppressed.Furthermore, since the film, which lowers the interface state, isdisposed on the light-receiving surface of the light-receiving portion,generation of electrons resulting from the interface state is furthersuppressed, so that flowing of electrons, which serve as a dark current,resulting from the interface state into the light-receiving portion issuppressed. Moreover, since the film, which has a negative fixed charge,is used, the HAD structure can be formed without conducting ionimplantation and annealing.

A method for manufacturing a solid-state imaging device (secondmanufacturing method) according to the present invention ischaracterized in that the method for manufacturing a solid-state imagingdevice having a light-receiving portion, which photoelectricallyconverts incident light and which is disposed on a semiconductorsubstrate, includes the steps of forming an insulating film, whichtransmits the above-described incident light, on a light-receivingsurface of the above-described light-receiving portion and forming afilm, which applies a negative voltage, on the above-describedinsulating film, wherein a hole accumulation layer is formed on thelight-receiving surface side of the above-described light-receivingportion by applying a negative voltage to the above-described film whichapplies a negative voltage.

In the above-described method for manufacturing a solid-state imagingdevice (second manufacturing method), since the film which applies anegative voltage, is disposed on the insulating film disposed on thelight-receiving surface of the light-receiving portion, the holeaccumulation (hole accumulation) layer is formed adequately at theinterface on the light-receiving surface side of the light-receivingportion by an electric field generated through application of a negativevoltage to the film, which applies a negative voltage. Therefore,generation of electric charges (electrons) from the interface issuppressed and, in addition, even when electric charges (electrons) aregenerated, the electric charges do not flow into a charge storageportion serving as a potential well in the light-receiving portion, flowthrough the hole accumulation layer, in which many holes are present,and can be extinguished. Consequently, it can be prevented that a darkcurrent due to the electric charges resulting from the interface isdetected by the light-receiving portion and a dark current resultingfrom the interface state can be suppressed. Moreover, since the film,which has a negative fixed charge, is used, the HAD structure can beformed without conducting ion implantation and annealing.

A method for manufacturing a solid-state imaging device (thirdmanufacturing method) according to the present invention ischaracterized in that the method for manufacturing a solid-state imagingdevice having a light-receiving portion, which photoelectricallyconverts incident light and which is disposed on a semiconductorsubstrate, includes the steps of forming an insulating film as an upperlayer on the light-receiving surface side of the above-describedlight-receiving portion and forming a film, which has a value of workfunction larger than that of the interface on the light-receivingsurface side of the above-described light-receiving portion to conductphotoelectric conversion, on the above-described insulating film.

In the above-described method for manufacturing a solid-state imagingdevice (third manufacturing method), since the film, which has a valueof work function larger than that of the interface on thelight-receiving surface side of the light-receiving portion to conductphotoelectric conversion, is formed on the insulating film disposed onthe light-receiving portion, a hole accumulation layer disposed at theinterface on the light-receiving side of the light-receiving portion canbe formed. Consequently, a dark current is reduced.

An imaging apparatus (first imaging apparatus) according to the presentinvention is characterized by including an light-condensing opticalportion, which condenses incident light, a solid-state imaging device,which receives and photoelectrically converts the above-describedincident light condensed in the above-described light-condensing opticalportion, and a signal processing portion, which processes aphotoelectrically converted signal charge, wherein the above-describedsolid-state imaging device includes a film, which is disposed on alight-receiving surface of a light-receiving portion of theabove-described solid-state imaging device to photoelectrically convertthe above-described incident light and which lowers an interface state,and a film, which is disposed on the above-described film to lower theinterface state and which has a negative fixed charge, wherein a holeaccumulation layer is disposed on the light-receiving surface of theabove-described light-receiving portion.

In the above-described first imaging apparatus, since theabove-described first solid-state imaging device according to thepresent invention is used, the solid-state imaging device, in which adark current is reduced, is used.

An imaging apparatus (second imaging apparatus) according to the presentinvention is characterized by including an light-condensing opticalportion, which condenses incident light, a solid-state imaging device,which receives and photoelectrically converts the above-describedincident light condensed in the above-described light-condensing opticalportion, and a signal processing portion, which processes aphotoelectrically converted signal charge, wherein the above-describedsolid-state imaging device includes an insulating film, which isdisposed on a light-receiving surface of a light-receiving portion ofthe above-described solid-state imaging device to photoelectricallyconvert the above-described incident light, and a film, which isdisposed on the above-described insulating film and which applies anegative voltage, the above-described insulating film is formed from aninsulating film, which transmits the above-described incident light, anda hole accumulation layer is disposed on the light-receiving surface ofthe above-described light-receiving portion.

In the above-described second imaging apparatus, since theabove-described second solid-state imaging device according to thepresent invention is used, the solid-state imaging device, in which adark current is reduced, is used.

An imaging apparatus (third imaging apparatus) according to the presentinvention is characterized by including an light-condensing opticalportion, which condenses incident light, a solid-state imaging device,which receives and photoelectrically converts the above-describedincident light condensed in the above-described light-condensing opticalportion, and a signal processing portion, which processes aphotoelectrically converted signal charge, wherein the above-describedsolid-state imaging device includes an insulating film, which isdisposed as an upper layer on a light-receiving surface side of alight-receiving portion to photoelectrically convert the incident lightto a signal charge, and a film, which is disposed on the above-describedinsulating film and which has a value of work function larger than thatof the interface on the light-receiving surface side of thelight-receiving portion to conduct photoelectric conversion.

In the above-described third imaging apparatus, since theabove-described third solid-state imaging device according to thepresent invention is used, the solid-state imaging device, in which adark current is reduced, is used.

According to the solid-state imaging device of the present invention, adark current can be suppressed and, thereby, noise in an image acquiredthrough imaging can be reduced. Therefore, there is an advantage that animage having high image quality can be obtained. In particular, anoccurrence of white point (point of a primary color in color CCD) due toa dark current in long-time exposure with a small amount of exposure canbe reduced.

According to the method for manufacturing a solid-state imaging deviceof the present invention, a dark current can be suppressed and, thereby,noise in an image acquired through imaging can be reduced. Therefore,there is an advantage that a solid-state imaging device capable ofobtaining an image having high image quality can be realized. Inparticular, a solid-state imaging device capable of reducing anoccurrence of white point (point of a primary color in color CCD) due toa dark current in long-time exposure with a small amount of exposure canbe realized.

According to the imaging apparatus of the present invention, since thesolid-state imaging device capable of suppressing a dark current isused, noise in an image acquired through imaging can be reduced.Therefore, there is an advantage that an image having high image qualitycan be obtained. In particular, an occurrence of white point (point of aprimary color in color CCD) due to a dark current in long-time exposurewith a small amount of exposure can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a key portion configuration sectional view showing anembodiment (first example) of a solid-state imaging device (firstsolid-state imaging device) according to the present invention.

FIG. 2 is an energy band diagram for explaining effects of thesolid-state imaging device (first solid-state imaging device) accordingto the present invention.

FIG. 3 is a key portion configuration sectional view showing a modifiedexample of the above-described solid-state imaging device (firstsolid-state imaging device) 1.

FIG. 4 is a key portion configuration sectional view showing a modifiedexample of the above-described solid-state imaging device (firstsolid-state imaging device) 1.

FIG. 5 is a key portion configuration sectional view for explaining theaction of a negative fixed charge in the case where a film, which hasthe negative fixed charge, is present in the vicinity of a peripheralcircuit portion.

FIG. 6 is a key portion configuration sectional view showing anembodiment (second example) of the solid-state imaging device (firstsolid-state imaging device) according to the present invention.

FIG. 7 is a key portion configuration sectional view showing anembodiment (third example) of the solid-state imaging device (firstsolid-state imaging device) according to the present invention.

FIG. 8 is a production step sectional view showing an embodiment (firstexample) of a method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 9 is a production step sectional view showing an embodiment (firstexample) of the method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 10 is a production step sectional view showing an embodiment (firstexample) of the method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 11 is a production step sectional view showing an embodiment(second example) of the method for manufacturing a solid-state imagingdevice (first manufacturing method) according to the present invention.

FIG. 12 is a production step sectional view showing an embodiment(second example) of the method for manufacturing a solid-state imagingdevice (first manufacturing method) according to the present invention.

FIG. 13 is a production step sectional view showing an embodiment(second example) of the method for manufacturing a solid-state imagingdevice (first manufacturing method) according to the present invention.

FIG. 14 is a production step sectional view showing an embodiment (thirdexample) of the method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 15 is a production step sectional view showing an embodiment (thirdexample) of the method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 16 is a production step sectional view showing an embodiment (thirdexample) of the method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 17 is a production step sectional view showing an embodiment(fourth example) of the method for manufacturing a solid-state imagingdevice (first manufacturing method) according to the present invention.

FIG. 18 is a production step sectional view showing an embodiment(fourth example) of the method for manufacturing a solid-state imagingdevice (first manufacturing method) according to the present invention.

FIG. 19 is a production step sectional view showing an embodiment(fourth example) of the method for manufacturing a solid-state imagingdevice (first manufacturing method) according to the present invention.

FIG. 20 is a production step sectional view showing an embodiment (fifthexample) of the method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 21 is a production step sectional view showing an embodiment (fifthexample) of the method for manufacturing a solid-state imaging device(first manufacturing method) according to the present invention.

FIG. 22 is a relationship diagram between the flat band voltage and thefilm thickness in terms of oxide film showing that a negative fixedcharge is present in a hafnium oxide (HfO₂) film.

FIG. 23 is a comparison diagram between interface state densitiesshowing that a negative fixed charge is present in a hafnium oxide(HfO₂) film.

FIG. 24 is a relationship diagram between the flat band voltage and thefilm thickness in terms of oxide film for explaining formation ofelectrons (electrons) and formation of holes (holes) with reference to athermal oxide film.

FIG. 25 is a key portion configuration sectional view showing anembodiment (first example) of a solid-state imaging device (secondsolid-state imaging device) according to the present invention.

FIG. 26 is a key portion configuration sectional view showing anembodiment (second example) of the solid-state imaging device (secondsolid-state imaging device) according to the present invention.

FIG. 27 is a production step sectional view showing an embodiment (firstexample) of a method for manufacturing a solid-state imaging device(second manufacturing method) according to the present invention.

FIG. 28 is a production step sectional view showing an embodiment (firstexample) of the method for manufacturing a solid-state imaging device(second manufacturing method) according to the present invention.

FIG. 29 is a production step sectional view showing an embodiment (firstexample) of the method for manufacturing a solid-state imaging device(second manufacturing method) according to the present invention.

FIG. 30 is a production step sectional view showing an embodiment(second example) of the method for manufacturing a solid-state imagingdevice (second manufacturing method) according to the present invention.

FIG. 31 is a production step sectional view showing an embodiment(second example) of the method for manufacturing a solid-state imagingdevice (second manufacturing method) according to the present invention.

FIG. 32 is a key portion configuration sectional view showing anembodiment (example) of a solid-state imaging device (third solid-stateimaging device) according to the present invention.

FIG. 33 is a key portion configuration sectional view showing an exampleof the configuration of a solid-state imaging device including a holeaccumulation auxiliary film.

FIG. 34 is a flow chart showing an embodiment (third example) of amethod for manufacturing a solid-state imaging device (thirdmanufacturing method) according to the present invention.

FIG. 35 is a production step sectional view showing an embodiment (thirdexample) of the method for manufacturing a solid-state imaging device(third manufacturing method) according to the present invention.

FIG. 36 is a production step sectional view showing an embodiment (thirdexample) of the method for manufacturing a solid-state imaging device(third manufacturing method) according to the present invention.

FIG. 37 is a block diagram showing an embodiment (example) of a imagingapparatus according to the present invention.

FIG. 38 is a schematic configuration sectional view of a light-receivingportion, showing a technique to suppress generation of a dark currentresulting from an interface state.

BEST MODES FOR CARRYING OUT THE INVENTION

An embodiment (first example) of a solid-state imaging device (firstsolid-state imaging device) according to the present invention will bedescribed with reference to a key portion configuration sectional viewshown in FIG. 1.

As shown in FIG. 1, a solid-state imaging device 1 has a light-receivingportion 12, which photoelectrically converts incident light L, on asemiconductor substrate (or a semiconductor layer) 11 and has aperipheral circuit portion 14 provided with a peripheral circuit (notspecifically shown in the drawing) in the portion beside thislight-receiving portion 12 with a pixel isolation region 13therebetween. In this regard, in the following explanation, theexplanation is made on the semiconductor substrate 11. A film 21, whichlowers an interface state, is disposed on a light-receiving surface 12 sof the above-described light-receiving portion (including a holeaccumulation layer 23 described later) 12. This film 21, which lowers aninterface state, is formed from, for example, a silicon oxide (SiO₂)film. A film 22, which has a negative fixed charge, is disposed on theabove-described film 21, which lowers an interface state. The holeaccumulation layer 23 is formed thereby on the light-receiving surfaceside of the above-described light-receiving portion 12. Therefore, atleast on the light-receiving portion 12, the above-described film 21,which lowers an interface state, is disposed having such a filmthickness that allows the hole accumulation layer 23 to be formed on thelight-receiving surface 12 s side of the above-described light-receivingportion 12 because of the above-described film 22, which has a negativefixed charge. The film thickness thereof is specified to be, forexample, 1 atomic layer or more, and 100 nm or less.

In the case where the above-described solid-state imaging device 1 is aCMOS image sensor, examples of peripheral circuits of theabove-described peripheral circuit portion 14 include pixel circuitscomposed of transistors, e.g., a transfer transistor, a resettransistor, an amplifying transistor, and a selection transistor.Furthermore, a drive circuit to effect an operation to read signals oflines to be read in a pixel array portion composed of a plurality oflight-receiving portions 12, a vertical scanning circuit to transfer thesignals read, a shift register or an address decoder, a horizontalscanning circuit, and the like are included.

Alternatively, in the case where the above-described solid-state imagingdevice 1 is a CCD image sensor, examples of peripheral circuits of theabove-described peripheral circuit portion 14 include a read gate, whichreads photoelectrically converted signal charges from thelight-receiving portion to a vertical transfer gate, and a verticalcharge transfer portion, which transfers read signal charges in thevertical direction. Furthermore, a horizontal charge transfer portionand the like are included.

The above-described film 22, which has a negative fixed charge, isformed from, for example, a hafnium oxide (HfO₂) film, an aluminum oxide(Al₂O₃) film, a zirconium oxide (ZrO₂) film, a tantalum oxide (Ta₂O₅)film, or a titanium oxide (TiO₂) film. The above-described films of thetypes mentioned above have a track record in being used for gateinsulating films or the like of insulated gate type field-effecttransistors. Therefore, the film formation method has been established,and film formation can be conducted easily. Examples of film formationmethods include a chemical vapor deposition method, a sputtering method,and an atomic layer deposition method. However, use of the atomic layerdeposition method is favorable because about 1 nm of SiO₂ layer, whichreduces an interface state, can be formed at the same time during filmformation. In this regard, examples of the materials other than thosedescribed above include lanthanum oxide (La₂O₃), praseodymium oxide(PrO₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethium oxide(Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), gadoliniumoxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide (Dy₂O₃), holmiumoxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide (Tm₂O₃), ytterbiumoxide (Yb₂O₃), lutetium oxide (Lu₂O₃), and yttrium oxide (Y₂O₃).Moreover, the above-described film 22, which has a negative fixedcharge, may also be formed from a hafnium nitride film, an aluminumnitride film, a hafnium oxynitride film, or an aluminum oxynitride film.

Regarding the above-described film 22, which has a negative fixedcharge, silicon (Si) or nitrogen (N) may be added to the film within thebounds of not impairing the insulating property. The concentrationthereof is determined appropriately within the bounds of not impairingthe insulating property of the film. In the case where silicon (Si) ornitrogen (N) is added as described above, it becomes possible to enhancethe heat resistance of the film and the capability of preventing ionimplantation during a process.

An insulating film 41 is disposed on the above-described film 22, whichhas a negative fixed charge, and a light-shield film 42 is disposed onthe above-described insulating film 41 above the above-describedperipheral circuit portion 14. A region, into which no light enters, isformed in the light-receiving portion 12 by this light-shield film 42,and a black level of the image is determined on the basis of an outputof the light-receiving portion 12. Moreover, since entrance of lightinto the peripheral circuit portion 14 is prevented, variations incharacteristics due to entrance of light into the peripheral circuitportion are suppressed. In addition, an insulating film 43, which has atransmission property with respect to the above-described incident lightis disposed. It is preferable that the surface of this insulating film43 is flattened. Furthermore, a color filter layer 44 and a condenserlens 45 are disposed on the insulating film 43.

In the above-described solid-state imaging device (first solid-stateimaging device) 1, the film 22, which has a negative fixed charge, isdisposed on the film 21, which lowers an interface state. Therefore, anelectric field is applied to the surface of the light-receiving portion12 by the negative fixed charge in the film of the film 22, which has anegative fixed charge, through the film 21, which lowers an interfacestate, and thereby, the hole accumulation (hole accumulation) layer 23is formed on the surface of the light-receiving portion 12.

Then, as shown in FIG. 2 (1), the vicinity of the interface can be madeinto the hole accumulation layer 23 because of an electric field due tothe negative fixed charge present in the film 22, which has a negativefixed charge, from immediately after formation of the film.Consequently, a dark current generated because of the interface state atthe interface between the light-receiving portion 12 and the film 21,which lowers an interface state, can be suppressed. That is, electriccharges (electrons) generated from the interface are reduced and, inaddition, even when electric charges (electrons) are generated from theinterface, the electric charges flow in the hole accumulation layer 23,in which many holes are present, and can be extinguished without flowinginto a charge accumulation portion, which serves as a potential well inthe light-receiving portion 12. Consequently, it can be prevented that adark current due to the electric charges resulting from the interface isdetected by the light-receiving portion 12 and, thereby, a dark currentresulting from the interface state can be suppressed.

On the other hand, as shown in FIG. 2 (2), in the configuration in whicha hole accumulation layer is not disposed, a problem occurs in that adark current is generated because of the interface state and theresulting dark current flows into the light-receiving portion 12.Furthermore, as shown in FIG. 2 (3), in the configuration in which thehole accumulation layer 23 is formed through ion implantation, as isdescribed above, although the hole accumulation layer 23 is formed, aheat treatment at a high temperature of 700° C. or higher isindispensable to activate the doping impurity in ion implantation, sothat diffusion of impurities occurs, the hole accumulation layer at theinterface is extended, a region for photoelectric conversion is reduced,and it becomes difficult to obtain desired photoelectric conversioncharacteristics.

Furthermore, in the above-described solid-state imaging device 1, sincethe film 21, which lowers the interface state, is disposed on thelight-receiving surface 12 s of the light-receiving portion 12,generation of electrons resulting from the interface state is furthersuppressed, so that flowing of electrons, which serve as a dark current,resulting from the interface state into the light-receiving portion 12is suppressed.

Moreover, in the case where a hafnium oxide film is used as the film 22,which has a negative fixed charge, since the refractive index of thehafnium oxide film is about 2, it is possible to not only form the HADstructure, but also obtain an antireflection effect at the same time byoptimizing the film thickness. Regarding materials other than thehafnium oxide film as well, as for materials having high refractiveindices, it is possible to obtain an antireflection effect by optimizingthe film thickness thereof.

In this regard, it is known that in the case where silicon oxide orsilicon nitride, which have been previously used in solid-state imagingdevices, is formed at low temperatures, the fixed charge in the filmbecomes positive, and it is not possible to form the HAD structure by anegative fixed charge.

Next, a modified example of the above-described solid-state imagingdevice (first solid-state imaging device) 1 will be described withreference to a key portion configuration sectional view shown in FIG. 3.

In the case where regarding the above-described solid-state imagingdevice 1, the antireflection effect on the light-receiving portion 12 byonly the film 22, which has a negative fixed charge, is inadequate,regarding a solid-state imaging device 2, as shown in FIG. 3, anantireflection film 46 is disposed on the film 22, which has a negativefixed charge. This antireflection film 46 is formed from, for example, asilicon nitride film. In this connection, the insulating film 43, whichis formed in the above-described solid-state imaging device 1, is notdisposed. Consequently, a color filter 44 and a condenser lens 45 aredisposed on the antireflection film 46. As described above, theantireflection effect can be maximized by forming a silicon nitride filmadditionally. This configuration can be applied to a solid-state imagingdevice 3 described next.

In the case where the antireflection film 46 is disposed as describedabove, reflection before entrance into the light-receiving portion 12can be reduced and, thereby, the amount of light incident on thelight-receiving portion 12 can be increased, so that the sensitivity ofthe solid-state imaging device 2 can be improved.

Next, a modified example of the above-described solid-state imagingdevice (first solid-state imaging device) 1 will be described withreference to a key portion configuration sectional view shown in FIG. 4.

Regarding a solid-state imaging device 3, as shown in FIG. 4, theabove-described insulating film 41, which is disposed in theabove-described solid-state imaging device 1, is not disposed, and theabove-described light-shield film 42 is disposed directly on the film22, which has a negative fixed charge. Furthermore, the antireflectionfilm 46 is disposed without disposing the insulating film 43.

In the case where the light-shield film 42 is disposed directly on thefilm 22, which has a negative fixed charge, as described above, thelight-shield film 42 can be made close to the surface of thesemiconductor substrate 11 and, thereby, the distance between thelight-shield film 42 and the semiconductor substrate 11 is reduced, sothat components of light incident slantingly from an upper layer of anadjacent light-receiving portion (photodiode), that is, optical colormixture components, can be reduced.

Furthermore, as shown in FIG. 5, in the case where the film 22, whichhas a negative fixed charge, is disposed in the vicinity on theperipheral circuit portion 14, a dark current resulting from theinterface state on the surface of the light-receiving portion 12 can besuppressed by the hole accumulation layer 23 formed from the negativefixed charge of the film 22, which has a negative fixed charge. However,in the peripheral circuit portion 14, a potential difference is allowedto be generated between the light-receiving portion 12 side and anelement 14D present on the surface side, and unexpected carriers flowfrom the surface of the light-receiving portion 12 into the element 14Dpresent on the surface side, so as to cause a malfunction of theperipheral circuit portion 14. A configuration to avoid such amalfunction will be described with reference to the following secondexample and third example.

Next, an embodiment (second example) of the solid-state imaging device(first solid-state imaging device) according to the present inventionwill be described with reference to a key portion configurationsectional view shown in FIG. 6.

In this regard, in FIG. 6, a light-shield film to shield a part of thelight-receiving portion and the peripheral circuit portion from light, acolor filter layer to disperse the light incident on the light-receivingportion, a condenser lens to condense the incident light on thelight-receiving portion, and the like are not shown in the drawing.

As shown in FIG. 6, in the solid-state imaging device 4, an insulatingfilm 24 is disposed between the surface of the above-describedperipheral circuit portion 14 and the above-described film 22, which hasa negative fixed charge, in such a way that the distance of theabove-described film 22, which has a negative fixed charge, from thesurface of the above-described peripheral circuit portion 14 in theabove-described solid-state imaging device 1 becomes larger than thedistance from the surface of the above-described light-receiving portion12. In the case where the above-described film 21, which lowers aninterface state, is formed from a silicon oxide film, this insulatingfilm 24 may be formed from the film 21, which lowers an interface stateand which has a thickness thereof on the peripheral circuit portion 14larger than the thickness thereof on the light-receiving portion 12.

As described above, the insulating film 24 is disposed between thesurface of the above-described peripheral circuit portion 14 and theabove-described film 22, which has a negative fixed charge, in such away that the distance of the above-described film 22, which has anegative fixed charge, from the surface of the above-describedperipheral circuit portion 14 becomes larger than the distance from thesurface of the above-described light-receiving portion 12. Therefore, inthe peripheral circuit portion 14, the influence of the electric fieldof a negative fixed charge in the film 22, which has a negative fixedcharge, is not exerted on the peripheral circuit. Consequently, amalfunction of the peripheral circuit due to the negative fixed chargecan be prevented.

Next, an embodiment (third example) of the solid-state imaging device(first solid-state imaging device) will be described with reference to akey portion configuration sectional view shown in FIG. 7. In thisregard, in FIG. 7, a light-shield film to shield a part of thelight-receiving portion and the peripheral circuit portion from light, acolor filter layer to disperse the light incident on the light-receivingportion, a condenser lens to condense the incident light on thelight-receiving portion, and the like are not shown in the drawing.

As shown in FIG. 7, in the solid-state imaging device 5, a film 25 toincrease the distance between the film, which has a negative fixedcharge, and the light-receiving surface is disposed above theabove-described peripheral circuit portion 14 and under theabove-described film 22, which has a negative fixed charge, in theabove-described solid-state imaging device 1. It is desirable that theabove-described film 25 has a positive fixed charge to cancel theinfluence of the negative fixed charge, and it is preferable thatsilicon nitride is used.

As described above, the above-described film 25, which has a positivefixed charge, is disposed above the above-described peripheral circuitportion 14 and under the above-described film 22, which has a negativefixed charge. Therefore, the negative fixed charge of the film 22, whichhas a negative fixed charge, is reduced by the positive fixed charge inthe above-described film 25, so that the influence of the electric fieldof a negative fixed charge in the film 22, which has the negative fixedcharge, is not exerted on the peripheral circuit portion 14.Consequently, a malfunction of the peripheral circuit 14 due to thenegative fixed charge can be prevented. The above-describedconfiguration, in which the above-described film 25 having a positivefixed charge is disposed above the above-described peripheral circuitportion 14 and under the above-described film 22 having a negative fixedcharge, can be applied to the above-described solid-state imagingdevices 1, 2, 3, and 4, and the effects similar to those of thesolid-state imaging device 5 can be obtained.

In the configuration on the film 22, which has a negative fixed charge,in the above-described solid-state imaging devices 4 and 5, thelight-shield film to shield a part of the light-receiving portion 12 andthe peripheral circuit portion 14 from light, the color filter layer todisperse the light incident on at least the light-receiving portion 12,the condenser lens to condense the incident light on the light-receivingportion 12, and the like are disposed. As an example of theconfiguration, any one of the configurations of the above-describedsolid-state imaging devices 1, 2, and 3 can also be applied.

Next, an embodiment (first example) of a method for manufacturing asolid-state imaging device (first manufacturing method) according to thepresent invention will be described with reference to production stepsectional views of a key portion shown in FIG. 8 to FIG. 10. In FIG. 8to FIG. 10, production steps of the above-described solid-state imagingdevice 1 are shown as an example.

As shown in FIG. 8 (1), the light-receiving portion 12, whichphotoelectrically converts incident light, the pixel isolation regions13, which isolate the light-receiving portion 12, the peripheral circuitportion 14, in which a peripheral circuit (not specifically shown in thedrawing) is disposed opposing to the light-receiving portion 12 with thepixel isolation region 13 therebetween, and the like are formed on thesemiconductor substrate (or semiconductor layer) 11. As for thismanufacturing method, a manufacturing method in the public domain isused.

Subsequently, as shown in FIG. 8 (2), the film 21, which lowers aninterface state, is formed on the light-receiving surface 12 s of theabove-described light-receiving portion 12, in actuality, on theabove-described semiconductor substrate 11. This film 21, which lowersan interface state, is formed from, for example, a silicon oxide (SiO₂)film. Then, the film 22, which has a negative fixed charge, is formed onthe above-described film 21, which lowers an interface state. The holeaccumulation layer 23 is formed thereby on the light-receiving surfaceside of the above-described light-receiving portion 12.

Therefore, at least on the light-receiving portion 12, it is necessarythat the above-described film 21, which lowers an interface state, isformed having a film thickness to allow the hole accumulation layer 23to be formed on the light-receiving surface 12 s side of theabove-described light-receiving portion 12 by the above-described film22, which has a negative fixed charge. The film thickness thereof isspecified to be, for example, 1 atomic layer or more, and 100 nm orless.

The above-described film 22, which has a negative fixed charge, isformed from, for example, a hafnium oxide (HfO₂) film, an aluminum oxide(Al₂O₃) film, a zirconium oxide (ZrO₂) film, a tantalum oxide (Ta₂O₅)film, or a titanium oxide (TiO₂) film. The above-described films of thetypes mentioned above have a track record in being used for gateinsulating films or the like of insulated gate type field-effecttransistors. Therefore, the film formation method has been established,and film formation can be conducted easily. As for the film formationmethod, for example, a chemical vapor deposition method, a sputteringmethod, and an atomic layer deposition method can be used. However, useof the atomic layer deposition method is favorable because about 1 nm ofSiO₂ layer, which reduces an interface state, can be formed at the sametime during film formation.

In this regard, examples of the usable materials other than thosedescribed above include lanthanum oxide (La₂O₃), praseodymium oxide(Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethium oxide(Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), gadoliniumoxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide (Dy₂O₃), holmiumoxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide (Tm₂O₃), ytterbiumoxide (Yb₂O₃), lutetium oxide (Lu₂O₃), and yttrium oxide (Y₂O₃).Moreover, the above-described film 22, which has a negative fixedcharge, can also be formed from a hafnium nitride film, an aluminumnitride film, a hafnium oxynitride film, or an aluminum oxynitride film.As for these films, for example, the chemical vapor deposition method,the sputtering method, the atomic layer deposition method, and the likecan also be used.

Furthermore, regarding the above-described film 22, which has a negativefixed charge, silicon (Si) or nitrogen (N) may be added to the filmwithin the bounds of not impairing the insulating property. Theconcentration thereof is determined appropriately within the bounds ofnot impairing the insulating property of the film. In the case wheresilicon (Si) or nitrogen (N) is added as described above, it becomespossible to enhance the heat resistance of the film and the capabilityof preventing ion implantation during a process.

Moreover, in the case where the above-described film 22, which has anegative fixed charge, is formed from a hafnium oxide (HfO₂) film, sincethe refractive index of the hafnium oxide (HfO₂) film is about 2, it ispossible to obtain an antireflection effect efficiently by adjusting thefilm thickness thereof. As a matter of course, regarding other types offilms as well, it is possible to obtain the antireflection effect byoptimizing the film thickness in accordance with the refractive index.

Subsequently, the insulating film 41 is formed on the above-describedfilm 22, which has a negative fixed charge, and in addition, thelight-shield film 42 is formed on the above-described insulating film41. The above-described insulating film 41 is formed from, for example,a silicon oxide film. In this connection, the above-describedlight-shield film 42 is formed from, for example, a metal film having alight-shielding property. In the case where the light-shield film 42 isformed on the above-described film 22, which has a negative fixedcharge, with the insulating film 41 therebetween, a reaction between thefilm 22, which is formed from a hafnium oxide film or the like and whichhas a negative fixed charge, and the metal in the light-shield film 42can be prevented. In addition, since the insulating film 41 serves as anetching stopper when the light-shield film is etched, etching damage tothe film 22, which has a negative fixed charge, can be prevented.

Next, as shown in FIG. 9 (3), a resist mask (not shown in the drawing)is formed on the above-described light-shield film 42 above a part ofthe above-described light-receiving portion 12 and the above-describedperipheral circuit portion 14 through resist application and thelithography technology, and the above-described light-shield film 42 isworked through etching by using the resist mask, so that thelight-shield film 42 is left on the above-described insulating film 41above a part of the above-described light-receiving portion 12 and theabove-described peripheral circuit portion 14. A region, into which nolight enters, is formed in the light-receiving portion 12 by theresulting light-shield film 42, and a black level of the image isdetermined on the basis of an output of the light-receiving portion 12.Furthermore, since entrance of light into the peripheral circuit portion14 is prevented, variations in characteristics due to entrance of lightinto the peripheral circuit portion are suppressed.

Subsequently, as shown in FIG. 9 (4), the insulating film 43 to reduce aheight difference due to the above-described light-shield film 42 isformed on the above-described insulating film 41. It is preferable thatthe surface of this insulating film 43 is flattened. The insulating film43 is formed from, for example, a coating insulating film.

Then, as shown in FIG. 10 (5), the color filter layer 44 is formed onthe insulating film 43 above the above-described light-receiving portion12 by a production technology in the public domain and, furthermore, thecondenser lens 45 is formed on the color filter layer 44. At that time,a light-transmitting insulating film (not shown in the drawing) may beformed between the color filter layer 44 and the condenser lens 45 inorder to prevent working damage to the color filter layer 44 during lensworking. In this manner, the solid-state imaging device 1 is formed.

In the first example of the above-described method for manufacturing asolid-state imaging device (first manufacturing method), since the film22, which has a negative fixed charge, is formed on the film 21, whichlowers an interface state, the hole accumulation (hole accumulation)layer 23 is formed adequately at the interface on the light-receivingsurface side of the light-receiving portion 12 by an electric fieldresulting from the negative fixed charge in the film 22, which has anegative fixed charge. Therefore, generation of electric charges(electrons) from the interface is suppressed and, in addition, even whenelectric charges (electrons) are generated, the electric charges do notflow into a charge storage portion serving as a potential well in thelight-receiving portion 12, flow through the hole accumulation layer 23,in which many holes are present, and can be extinguished. Consequently,it can be prevented that a dark current due to the electric chargesresulting from the interface is detected by the light-receiving portionand a dark current resulting from the interface state can be suppressed.Furthermore, since the film 21, which lowers the interface state, isdisposed on the light-receiving surface of the light-receiving portion12, generation of electrons resulting from the interface state isfurther suppressed, so that flowing of electrons, which serve as a darkcurrent, resulting from the interface state into the light-receivingportion 12 is suppressed. Moreover, since the film 22, which has anegative fixed charge, is used, the HAD structure can be formed withoutconducting ion implantation and annealing.

Next, an embodiment (second example) of the method for manufacturing asolid-state imaging device (first manufacturing method) according to thepresent invention will be described with reference to production stepsectional views of a key portion shown in FIG. 11 to FIG. 13. In FIG. 11to FIG. 13, production steps of the above-described solid-state imagingdevice 2 are shown as an example.

As shown in FIG. 11 (1), the light-receiving portion 12, whichphotoelectrically converts incident light, the pixel isolation regions13, which isolate the light-receiving portion 12, the peripheral circuitportion 14, in which a peripheral circuit (not specifically shown in thedrawing) is disposed opposing to the light-receiving portion 12 with thepixel isolation region 13 therebetween, and the like are formed on thesemiconductor substrate (or semiconductor layer) 11. As for thismanufacturing method, a manufacturing method in the public domain isused.

Subsequently, as shown in FIG. 11 (2), the film 21, which lowers aninterface state, is formed on the light-receiving surface 12 s of theabove-described light-receiving portion 12, in actuality, on theabove-described semiconductor substrate 11. This film 21, which lowersan interface state, is formed from, for example, a silicon oxide (SiO₂)film. Then, the film 22, which has a negative fixed charge, is formed onthe above-described film 21, which lowers an interface state. The holeaccumulation layer 23 is formed thereby on the light-receiving surfaceside of the above-described light-receiving portion 12. Therefore, atleast on the light-receiving portion 12, it is necessary that theabove-described film 21, which lowers an interface state, is formedhaving a film thickness to allow the hole accumulation layer 23 to beformed on the light-receiving surface 12 s side of the above-describedlight-receiving portion 12 by the above-described film 22, which has anegative fixed charge. The film thickness thereof is specified to be,for example, 1 atomic layer or more, and 100 nm or less.

The above-described film 22, which has a negative fixed charge, isformed from, for example, a hafnium oxide (HfO₂) film, an aluminum oxide(Al₂O₃) film, a zirconium oxide (ZrO₂) film, a tantalum oxide (Ta₂O₅)film, or a titanium oxide (TiO₂) film. The above-described films of thetypes mentioned above have a track record in being used for gateinsulating films or the like of insulated gate type field-effecttransistors. Therefore, the film formation method has been established,and film formation can be conducted easily. As for the film formationmethod, for example, a chemical vapor deposition method, a sputteringmethod, and an atomic layer deposition method can be used.

In this regard, examples of the usable materials other than thosedescribed above include lanthanum oxide (La₂O₃), praseodymium oxide(Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethium oxide(Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), gadoliniumoxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide (Dy₂O₃), holmiumoxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide (Tm₂O₃) ytterbiumoxide (Yb₂O₃), lutetium oxide (Lu₂O₃), and yttrium oxide (Y₂O₃).Moreover, the above-described film 22, which has a negative fixedcharge, can also be formed from a hafnium nitride film, an aluminumnitride film, a hafnium oxynitride film, or an aluminum oxynitride film.As for these films, for example, the chemical vapor deposition method,the sputtering method, the atomic layer deposition method, and the likecan also be used. However, use of the atomic layer deposition method isfavorable because about 1 nm of SiO₂ layer, which reduces an interfacestate, can be formed at the same time during film formation.

Furthermore, regarding the above-described film 22, which has a negativefixed charge, silicon (Si) or nitrogen (N) may be added to the filmwithin the bounds of not impairing the insulating property. Theconcentration thereof is determined appropriately within the bounds ofnot impairing the insulating property of the film. In the case wheresilicon (Si) or nitrogen (N) is added as described above, it becomespossible to enhance the heat resistance of the film and the capabilityof preventing ion implantation during a process.

Moreover, in the case where the above-described film 22, which has anegative fixed charge, is formed from a hafnium oxide (HfO₂) film, sincethe refractive index of the hafnium oxide (HfO₂) film is about 2, it ispossible to obtain an antireflection effect efficiently by adjusting thefilm thickness thereof. As a matter of course, regarding other types offilms as well, it is possible to obtain the antireflection effect byoptimizing the film thickness in accordance with the refractive index.

Subsequently, the insulating film 41 is formed on the above-describedfilm 22, which has a negative fixed charge, and in addition, thelight-shield film 42 is formed on the above-described insulating film41. The above-described insulating film 41 is formed from, for example,a silicon oxide film. In this connection, the above-describedlight-shield film 42 is formed from, for example, a metal film having alight-shielding property. In the case where the light-shield film 42 isformed on the above-described film 22, which has a negative fixedcharge, with the insulating film 41 therebetween, a reaction between thefilm 22, which is formed from a hafnium oxide film or the like and whichhas a negative fixed charge, and the metal in the light-shield film 42can be prevented. In addition, since the insulating film 41 serves as anetching stopper when the light-shield film is etched, etching damage tothe film 22, which has a negative fixed charge, can be prevented.

Next, as shown in FIG. 12 (3), a resist mask (not shown in the drawing)is formed on the above-described light-shield film 42 above a part ofthe above-described light-receiving portion 12 and the above-describedperipheral circuit portion 14 through resist application and thelithography technology, and the above-described light-shield film 42 isworked through etching by using the resist mask, so that thelight-shield film 42 is left on the above-described insulating film 41above a part of the above-described light-receiving portion 12 and theabove-described peripheral circuit portion 14. A region, into which nolight enters, is formed in the light-receiving portion 12 by theresulting light-shield film 42, and a black level of the image isdetermined on the basis of an output of the light-receiving portion 12.Furthermore, since entrance of light into the peripheral circuit portion14 is prevented, variations in characteristics due to entrance of lightinto the peripheral circuit portion are suppressed.

Then, as shown in FIG. 12 (4), the antireflection film 46 is formed onthe above-described insulating film 41 in such a way as to cover theabove-described light-shield film 42. This antireflection film 46 isformed from, for example, a silicon nitride film having a refractiveindex of about 2.

Subsequently, as shown in FIG. 13 (5), the color filter layer 44 isformed on the antireflection film 46 above the above-describedlight-receiving portion 12 and, furthermore, the condenser lens 45 isformed on the color filter layer 44. At that time, a light-transmittinginsulating film (not shown in the drawing) may be formed between thecolor filter layer 44 and the condenser lens 45 in order to preventworking damage to the color filter layer 44 during lens working. In thismanner, the solid-state imaging device 2 is formed.

According to the second example of the above-described method formanufacturing a solid-state imaging device (first manufacturing method),the effects similar to those of the above-described first example can beobtained. In addition, since the antireflection film 46 is formed,reflection before entrance into the light-receiving portion 12 can bereduced and, thereby, the amount of light incident on thelight-receiving portion 12 can be increased, so that the sensitivity ofthe solid-state imaging device 2 can be improved.

Next, an embodiment (third example) of the method for manufacturing asolid-state imaging device (first manufacturing method) according to thepresent invention will be described with reference to production stepsectional views of a key portion shown in FIG. 14 to FIG. 16. In FIG. 14to FIG. 16, production steps of the above-described solid-state imagingdevice 3 are shown as an example.

As shown in FIG. 14 (1), the light-receiving portion 12, whichphotoelectrically converts incident light, the pixel isolation regions13, which isolate the light-receiving portion 12, the peripheral circuitportion 14, in which a peripheral circuit (not specifically shown in thedrawing) is disposed opposing to the light-receiving portion 12 with thepixel isolation region 13 therebetween, and the like are formed on thesemiconductor substrate (or semiconductor layer) 11. As for thismanufacturing method, a manufacturing method in the public domain isused.

Subsequently, as shown in FIG. 14 (2), the film 21, which lowers aninterface state, is formed on the light-receiving surface 12 s of theabove-described light-receiving portion 12, in actuality, on theabove-described semiconductor substrate 11. This film 21, which lowersan interface state, is formed from, for example, a silicon oxide (SiO₂)film. Then, the film 22, which has a negative fixed charge, is formed onthe above-described film 21, which lowers an interface state. The holeaccumulation layer 23 is formed thereby on the light-receiving surfaceside of the above-described light-receiving portion 12. Therefore, atleast on the light-receiving portion 12, it is necessary that theabove-described film 21, which lowers an interface state, is formedhaving a film thickness to allow the hole accumulation layer 23 to beformed on the light-receiving surface 12 s side of the above-describedlight-receiving portion 12 by the above-described film 22, which has anegative fixed charge. The film thickness thereof is specified to be,for example, 1 atomic layer or more, and 100 nm or less.

The above-described film 22, which has a negative fixed charge, isformed from, for example, a hafnium oxide (HfO₂) film, an aluminum oxide(Al₂O₃) film, a zirconium oxide (ZrO₂) film, a tantalum oxide (Ta₂O₅film, or a titanium oxide (TiO₂) film. The above-described films of thetypes mentioned above have a track record in being used for gateinsulating films or the like of insulated gate type field-effecttransistors. Therefore, the film formation method has been established,and film formation can be conducted easily. As for the film formationmethod, for example, a chemical vapor deposition method, a sputteringmethod, and an atomic layer deposition method can be used. However, useof the atomic layer deposition method is favorable because about 1 nm ofSiO₂ layer, which reduces an interface state, can be formed at the sametime during film formation.

In this regard, examples of the usable materials other than thosedescribed above include lanthanum oxide (La₂O₃), praseodymium oxide(Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethium oxide(Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), gadoliniumoxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide (Dy₂O₃), holmiumoxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide (Tm₂O₃), ytterbiumoxide (Yb₂O₃), lutetium oxide (Lu₂O₃), and yttrium oxide (Y₂O₃).Moreover, the above-described film 22, which has a negative fixedcharge, can also be formed from a hafnium nitride film, an aluminumnitride film, a hafnium oxynitride film, or an aluminum oxynitride film.As for these films, for example, the chemical vapor deposition method,the sputtering method, the atomic layer deposition method, and the likecan also be used.

Furthermore, regarding the above-described film 22, which has a negativefixed charge, silicon (Si) or nitrogen (N) may be added to the filmwithin the bounds of not impairing the insulating property. Theconcentration thereof is determined appropriately within the bounds ofnot impairing the insulating property of the film. In the case wheresilicon (Si) or nitrogen (N) is added as described above, it becomespossible to enhance the heat resistance of the film and the capabilityof preventing ion implantation during a process.

Moreover, in the case where the above-described film 22, which has anegative fixed charge, is formed from a hafnium oxide (HfO₂) film, it ispossible to obtain an antireflection effect efficiently by adjusting thefilm thickness of the hafnium oxide (HfO₂) film. As a matter of course,regarding other types of films as well, it is possible to obtain theantireflection effect by optimizing the film thickness in accordancewith the refractive index.

Then, the light-shield film 42 is formed on the above-described film 22,which has a negative fixed charge. The above-described light-shield film42 is formed from, for example, a metal film having a light-shieldingproperty. In the case where the light-shield film 42 is formed directlyon the film 22, which has a negative fixed charge, as described above,the light-shield film 42 can be made close to the surface of thesemiconductor substrate 11 and, thereby, the distance between thelight-shield film 42 and the semiconductor substrate 11 is reduced, sothat components of light incident slantingly from an upper layer of anadjacent photodiode, that is, optical color mixture components, can bereduced.

Next, as shown in FIG. 15 (3), a resist mask (not shown in the drawing)is formed on the above-described light-shield film 42 above a part ofthe above-described light-receiving portion 12 and the above-describedperipheral circuit portion 14 through resist application and thelithography technology, and the above-described light-shield film 42 isworked through etching by using the resist mask, so that thelight-shield film 42 is left on the above-described film 22, which has anegative fixed charge, above a part of the above-describedlight-receiving portion 12 and the above-described peripheral circuitportion 14. A region, into which no light enters, is formed in thelight-receiving portion 12 by the resulting light-shield film 42, and ablack level of the image is determined on the basis of an output of thelight-receiving portion 12. Furthermore, since entrance of light intothe peripheral circuit portion 14 is prevented, variations incharacteristics due to entrance of light into the peripheral circuitportion are suppressed.

Thereafter, as shown in FIG. 15 (4), the antireflection film 46 isformed on the above-described film 22, which has a negative fixedcharge, in such a way as to cover the above-described light-shield film42. This antireflection film 46 is formed from, for example, a siliconnitride film having a refractive index of about 2.

Subsequently, as shown in FIG. 16 (5), the color filter layer 44 isformed on the antireflection film 46 above the above-describedlight-receiving portion 12 and, furthermore, the condenser lens 45 isformed on the color filter layer 44. At that time, a light-transmittinginsulating film (not shown in the drawing) may be formed between thecolor filter layer 44 and the condenser lens 45 in order to preventworking damage to the color filter layer 44 during lens working. In thismanner, the solid-state imaging device 3 is formed.

According to the third example of the above-described method formanufacturing a solid-state imaging device (first manufacturing method),the effects similar to those of the above-described first example can beobtained. In addition, since the light-shield film 42 is formed directlyon the film 22, which has a negative fixed charge, the light-shield film42 can be made close to the surface of the semiconductor substrate 11and, thereby, the distance between the light-shield film 42 and thesemiconductor substrate 11 is reduced, so that components of lightincident slantingly from an upper layer of an adjacent photodiode, thatis, optical color mixture components, can be reduced. Furthermore, sincethe antireflection film 46 is formed, the antireflection effect can bemaximized in the case where the antireflection effect by only the film22, which has a negative fixed charge, is inadequate.

Next, an embodiment (fourth example) of the method for manufacturing asolid-state imaging device (first manufacturing method) according to thepresent invention will be described with reference to production stepsectional views of a key portion shown in FIG. 17 to FIG. 19. In FIG. 17to FIG. 19, production steps of the above-described solid-state imagingdevice 4 are shown as an example.

As shown in FIG. 17 (1), the light-receiving portions 12, whichphotoelectrically convert incident light, the pixel isolation regions13, which isolate the light-receiving portions 12, the peripheralcircuit portion 14, in which a peripheral circuit (for example, acircuit 14C) is disposed opposing to the light-receiving portion 12 withthe pixel isolation region 13 therebetween, and the like are formed onthe semiconductor substrate (or semiconductor layer) 11. As for thismanufacturing method, a manufacturing method in the public domain isused. Subsequently, an insulating film 26, which has alight-transmitting property with respect to the above-described incidentlight, is formed. This insulating film 26 is formed from, for example, asilicon oxide film.

Then, as shown in FIG. 17 (2), a resist mask 51 is formed on theabove-described insulating film 26 above the above-described peripheralcircuit portion 14 through resist application and the lithographytechnology.

Thereafter, as shown in FIG. 18 (3), the above-described insulating film26 is worked through etching by using the above-described resist mask 51(refer to FIG. 17 (2) described above), so that the insulating film 26is left on the above-described peripheral circuit portion 14.Subsequently, the above-described resist mask 51 is removed.

Next, as shown in FIG. 18 (4), the film 21, which covers theabove-described insulating film 26 and which lowers an interface state,is formed on the light-receiving surface 12 s of the above-describedlight-receiving portion 12, in actuality, on the above-describedsemiconductor substrate 11. This film 21, which lowers an interfacestate, is formed from, for example, a silicon oxide (SiO₂) film.

Then, as shown in FIG. 19 (5), the film 22, which has a negative fixedcharge, is formed on the above-described film 21, which lowers aninterface state. The hole accumulation layer 23 is formed thereby on thelight-receiving surface side of the above-described light-receivingportion 12. Therefore, at least on the light-receiving portion 12, it isnecessary that the above-described film 21, which lowers an interfacestate, is formed having a film thickness to allow the hole accumulationlayer 23 to be formed on the light-receiving surface 12 s side of theabove-described light-receiving portion 12 by the above-described film22, which has a negative fixed charge. The film thickness thereof isspecified to be, for example, 1 atomic layer or more, and 100 nm orless.

The above-described film 22, which has a negative fixed charge, isformed from, for example, a hafnium oxide (HfO₂) film, an aluminum oxide(Al₂O₃) film, a zirconium oxide (ZrO₂) film, a tantalum oxide (Ta₂O₅)film, or a titanium oxide (TiO₂) film. The above-described films of thetypes mentioned above have a track record in being used for gateinsulating films or the like of insulated gate type field-effecttransistors. Therefore, the film formation method has been established,and film formation can be conducted easily. As for the film formationmethod, for example, a chemical vapor deposition method, a sputteringmethod, and an atomic layer deposition method can be used. However, useof the atomic layer deposition method is favorable because about 1 nm ofSiO₂ layer, which reduces an interface state, can be formed at the sametime during film formation.

In this regard, examples of the usable materials other than thosedescribed above include lanthanum oxide (La₂O₃), praseodymium oxide(Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethium oxide(Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), gadoliniumoxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide (Dy₂O₃), holmiumoxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide (Tm₂O₃) ytterbiumoxide (Yb₂O₃), lutetium oxide (Lu₂O₃), and yttrium oxide (Y₂O₃).Moreover, the above-described film 22, which has a negative fixedcharge, can also be formed from a hafnium nitride film, an aluminumnitride film, a hafnium oxynitride film, or an aluminum oxynitride film.As for these films, for example, the chemical vapor deposition method,the sputtering method, the atomic layer deposition method, and the likecan also be used.

Furthermore, regarding the above-described film 22, which has a negativefixed charge, silicon (Si) or nitrogen (N) may be added to the filmwithin the bounds of not impairing the insulating property. Theconcentration thereof is determined appropriately within the bounds ofnot impairing the insulating property of the film. In the case wheresilicon (Si) or nitrogen (N) is added as described above, it becomespossible to enhance the heat resistance of the film and the capabilityof preventing ion implantation during a process.

Moreover, in the case where the above-described film 22, which has anegative fixed charge, is formed from a hafnium oxide (HfO₂) film, it ispossible to obtain an antireflection effect efficiently by adjusting thefilm thickness thereof because the refractive index of the hafnium oxide(HfO₂) film is about 2. As a matter of course, regarding other types offilms as well, it is possible to obtain the antireflection effect byoptimizing the film thickness in accordance with the refractive index.

In the configuration on the film 22, which has a negative fixed charge,in the above-described solid-state imaging device 4, the light-shieldfilm to shield a part of the light-receiving portion 12 and theperipheral circuit portion 14 from light, the color filter layer todisperse the light incident on at least the light-receiving portion 12,the condenser lens to condense the incident light on the light-receivingportion 12, and the like are disposed. As an example of theconfiguration, any one of the configurations of the above-describedsolid-state imaging devices 1, 2, and 3 can also be applied.

In the fourth example of the above-described method for manufacturing asolid-state imaging device (first manufacturing method), since the film22, which has a negative fixed charge, is formed on the film 21, whichlowers an interface state, the hole accumulation (hole accumulation)layer 23 is formed adequately at the interface on the light-receivingsurface side of the light-receiving portion 12 by an electric fieldresulting from the negative fixed charge in the film 22, which has anegative fixed charge. Therefore, generation of electric charges(electrons) from the interface is suppressed and, in addition, even whenelectric charges (electrons) are generated, the electric charges do notflow into a charge storage portion serving as a potential well in thelight-receiving portion 12, flow through the hole accumulation layer, inwhich many holes are present, and can be extinguished. Consequently, itcan be prevented that a dark current due to the electric chargesresulting from the interface is detected by the light-receiving portionand a dark current resulting from the interface state is suppressed.Furthermore, since the film 21, which lowers the interface state, isdisposed on the light-receiving surface of the light-receiving portion12, generation of electrons resulting from the interface state isfurther suppressed, so that flowing of electrons, which serve as a darkcurrent, resulting from the interface state into the light-receivingportion 12 is suppressed. Moreover, since the film 22, which has anegative fixed charge, is used, the HAD structure can be formed withoutconducting ion implantation and annealing.

In addition, since the insulating film 26 is disposed on the peripheralcircuit portion 14, the distance to the film 22, which has a negativefixed charge, on the peripheral circuit portion 14 becomes larger thanthe distance to the film, which has a negative fixed charge, on thelight-receiving portion 12. Therefore, the negative electric fieldapplied from the film 22, which has a negative fixed charge, to theperipheral circuit portion 14 is mitigated. That is, the influence ofthe film 22, which has a negative fixed charge, exerted on theperipheral circuit portion 14 is reduced. Consequently, a malfunction ofthe peripheral circuit portion 14 due to the negative electric field onthe basis of the film 22, which has a negative fixed charge, isprevented.

Next, an embodiment (fifth example) of the method for manufacturing asolid-state imaging device (first manufacturing method) according to thepresent invention will be described with reference to production stepsectional views of a key portion shown in FIG. 20 and FIG. 21. In FIG.20 and FIG. 21, production steps of the above-described solid-stateimaging device 5 are shown as an example.

As shown in FIG. 20 (1), the light-receiving portions 12, whichphotoelectrically convert incident light, the pixel isolation regions13, which isolate the light-receiving portions 12, the peripheralcircuit portion 14, in which a peripheral circuit (for example, acircuit 14C) is disposed opposing to the light-receiving portion 12 withthe pixel isolation region 13 therebetween, and the like are formed onthe semiconductor substrate (or semiconductor layer) 11. As for thismanufacturing method, a manufacturing method in the public domain isused. Subsequently, the film 21, which has a light-transmitting propertywith respect to the above-described incident light and which lowers theinterface state, is formed. This film 21, which lowers the interfacestate, is formed from, for example, a silicon oxide film. Furthermore, afilm 25 to keep the film, which has a negative fixed charge, away fromthe surface of the light-receiving surface is formed on theabove-described film 21, which lowers the interface state. It isdesirable that the above-described film 25 has a positive fixed chargeto cancel the influence of the negative fixed charge, and it ispreferable that silicon nitride is used.

At least on the light-receiving portion 12, it is necessary that theabove-described film 21, which lowers an interface state, is formedhaving a film thickness to allow the hole accumulation layer 23, whichwill be described later, to be formed on the light-receiving surface 12s side of the above-described light-receiving portion 12 by theabove-described film 22, which will be described later and which has anegative fixed charge. The film thickness thereof is specified to be,for example, 1 atomic layer or more, and 100 nm or less.

Then, as shown in FIG. 20 (2), a resist mask 52 is formed on theabove-described film 25, which has a positive fixed charge, above theabove-described peripheral circuit portion 14 through resist applicationand the lithography technology.

Thereafter, as shown in FIG. 21 (3), the above-described film 25, whichhas a positive fixed charge, is worked through etching by using theabove-described resist mask 52 (refer to FIG. 20 (2) described above),so that the above-described film 25, which has a positive fixed charge,is left on the above-described peripheral circuit portion 14.Subsequently, the above-described resist mask 52 is removed.

Next, as shown in FIG. 21 (4), the film 22, which covers theabove-described film 25 having a positive fixed charge and which has anegative fixed charge, is formed on the above-described film 21, whichlowers the interface state.

The above-described film 22, which has a negative fixed charge, isformed from, for example, a hafnium oxide (HfO₂) film, an aluminum oxide(Al₂O₃) film, a zirconium oxide (ZrO₂) film, a tantalum oxide (Ta₂O₅)film, or a titanium oxide (TiO₂) film. The above-described films of thetypes mentioned above have a track record in being used for gateinsulating films or the like of insulated gate type field-effecttransistors. Therefore, the film formation method has been established,and film formation can be conducted easily. As for the film formationmethod, for example, a chemical vapor deposition method, a sputteringmethod, and an atomic layer deposition method can be used. However, useof the atomic layer deposition method is favorable because about 1 nm ofSiO₂ layer, which reduces an interface state, can be formed at the sametime during film formation.

In this regard, examples of the usable materials other than thosedescribed above include lanthanum oxide (La₂O₃), praseodymium oxide(Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethium oxide(Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), gadoliniumoxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide (Dy₂O₃), holmiumoxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide (Tm₂O₃) ytterbiumoxide (Yb₂O₃), lutetium oxide (Lu₂O₃), and yttrium oxide (Y₂O₃).Moreover, the above-described film 22, which has a negative fixedcharge, can also be formed from a hafnium nitride film, an aluminumnitride film, a hafnium oxynitride film, or an aluminum oxynitride film.As for these films, for example, the chemical vapor deposition method,the sputtering method, the atomic layer deposition method, and the likecan also be used.

Furthermore, regarding the above-described film 22, which has a negativefixed charge, silicon (Si) or nitrogen (N) may be added to the filmwithin the bounds of not impairing the insulating property. Theconcentration thereof is determined appropriately within the bounds ofnot impairing the insulating property of the film. In the case wheresilicon (Si) or nitrogen (N) is added as described above, it becomespossible to enhance the heat resistance of the film and the capabilityof preventing ion implantation during a process.

Moreover, in the case where the above-described film 22, which has anegative fixed charge, is formed from a hafnium oxide (HfO₂) film, it ispossible to obtain an antireflection effect efficiently by adjusting thefilm thickness of the hafnium oxide (HfO₂) film. As a matter of course,regarding other types of films as well, it is possible to obtain theantireflection effect by optimizing the film thickness in accordancewith the refractive index.

In the configuration on the film 22, which has a negative fixed charge,in the above-described solid-state imaging device 5, the light-shieldfilm to shield a part of the light-receiving portion 12 and theperipheral circuit portion 14 from light, the color filter layer todisperse the light incident on at least the light-receiving portion 12,the condenser lens to condense the incident light on the light-receivingportion 12, and the like are disposed. As an example of theconfiguration, any one of the configurations of the above-describedsolid-state imaging devices 1, 2, and 3 can also be applied. In thefifth example of the above-described method for manufacturing asolid-state imaging device (first manufacturing method), since the film22, which has a negative fixed charge, is formed on the film 21, whichlowers an interface state, the hole accumulation (hole accumulation)layer 23 is formed adequately at the interface on the light-receivingsurface side of the light-receiving portion 12 by an electric fieldresulting from the negative fixed charge in the film 22, which has anegative fixed charge. Therefore, generation of electric charges(electrons) from the interface is suppressed and, in addition, even whenelectric charges (electrons) are generated, the electric charges do notflow into a charge storage portion serving as a potential well in thelight-receiving portion 12, flow through the hole accumulation layer 23,in which many holes are present, and can be extinguished. Consequently,it can be prevented that a dark current due to the electric chargesresulting from the interface is detected by the light-receiving portionand a dark current resulting from the interface state is suppressed.Furthermore, since the film 21, which lowers the interface state, isdisposed on the light-receiving surface of the light-receiving portion12, generation of electrons resulting from the interface state isfurther suppressed, so that flowing of electrons, which serve as a darkcurrent, resulting from the interface state into the light-receivingportion 12 is suppressed. Moreover, since the film 22, which has anegative fixed charge, is used, the HAD structure can be formed withoutconducting ion implantation and annealing.

In addition, since the film 25, which has preferably a positive fixedcharge and which keeps the film having a negative fixed charge away fromthe surface of the light-receiving surface, is disposed above theabove-described peripheral circuit portion 14 and under theabove-described film 22, which has a negative fixed charge, the negativefixed charge of the film 22, which has the negative charge, is reducedby the positive fixed charge in the film 25, which has the positivefixed charge, so that the influence due to the electric field of thenegative fixed charge in the film 22, which has the negative fixedcharge, is not exerted on the peripheral circuit portion 14.Consequently, a malfunction of the peripheral circuit portion 14 due tothe negative fixed charge can be prevented.

Here, regarding a hafnium oxide (HfO₂) film as an example of the film,which has a negative fixed charge, data indicating the presence of thenegative fixed charge will be described with reference to FIG. 22.

As for a first sample, MOS capacitors, in which a gate electrode wasformed on a silicon substrate with a thermal silicon oxide (SiO₂) filmtherebetween, were prepared, where the film thicknesses of theabove-described thermal silicon oxide films were changed.

As for a second sample, MOS capacitors, in which a gate electrode wasformed on a silicon substrate with a CVD silicon oxide (CVD-SiO₂) filmtherebetween, were prepared, where the film thicknesses of theabove-described CVD silicon oxide films were changed.

As for a third sample, MOS capacitors, in which a gate electrode wasformed on a silicon substrate with a laminated film composed ofsequentially laminated ozone silicon oxide (O₃—SiO₂) film, hafnium oxide(HfO₂) film, and CVD silicon oxide (SiO₂) film therebetween, wereprepared, where the film thicknesses of the above-described CVD siliconoxide films were changed. In this regard, the film thicknesses of theHfO₂ film and the O₃—SiO₂ film were fixed.

In each of the above-described samples, the CVD-SiO₂ film is formed by aCVD method through the use of a mixed gas of monosilane (SiH₄) andoxygen (O₂), and the HfO₂ film is formed by an ALD method in whichtetrakisethylmethyl-amino hafnium (tetrakisethylmethyl-amino hafnium:TEMAHf) and ozone (O₃) serve as raw materials. The O₃—SiO₂ film in theabove-described third sample is an interfacial oxide film, which isformed between HfO₂ and the silicon substrate by the ALD method in theformation of the HfO₂ film and which has a thickness of about 1 nm. Asfor every gate electrode in the above-described individual samples, astructure, in which an aluminum (Al) film, a titanium nitride (TiN)film, and a titanium (Ti) film are laminated in that order from theupper layer, is employed.

In this connection, regarding the above-described sample structures, inthe first sample and the second sample, the gate electrode is disposedimmediately above the SiO₂ film, whereas only the third sample includingthe HfO₂ film has the structure, in which the CVD-SiO₂ film is laminatedon the HfO₂ film. The reason therefor is that an occurrence of reactionbetween HfO₂ and the gate electrode at the interface is prevented bybringing HfO₂ into direct contact with the electrode.

Furthermore, in the laminated structure of the third sample, the HfO₂film thickness was fixed at 10 nm, and the film thickness of theCVD-SiO₂ film serving as an upper layer was changed. The reason thereforis that HfO₂ has a large specific dielectric constant and, therefore,even when a film thickness at a level of 10 nm is formed, the filmthickness in terms of oxide film is several nanometers. Consequently, itis difficult to observe changes in flat band voltage Vfb versus filmthickness in terms of oxide film.

Regarding the above-described first sample, second sample, and thirdsample, the film thickness Tox in terms of oxide film versus the flatband voltage Vfb was examined. The results thereof are shown in FIG. 22.

As shown in FIG. 22, regarding the first sample including the thermaloxide (Thermal-SiO₂) film and the second sample including the CVD-SiO₂film, the flat band voltage shifts in the negative direction along withan increase in film thickness. On the other hand, it is ascertained thatregarding only the third sample including the HfO₂ film, the flat bandvoltage shifts in the positive direction along with an increase in filmthickness. As is clear from this behavior of the flat band voltage, anegative charge is present in the film of the HfO₂ film. Moreover, ithas been known that the above-described individual materials, whichconstitute the films having negative fixed charges, other than HfO₂ havenegative fixed charges similarly to HfO₂.

In addition, the data of interface state densities of theabove-described individual samples are shown in FIG. 23. In this FIG.23, the interface state densities Dit are compared by using the firstsample, the second sample, and the third sample, which had nearly equalTox of about 40 nm in FIG. 22.

As a result, as shown in FIG. 23, the characteristic of the first sampleincluding the thermal oxide (Thermal-SiO₂) film is 2E10 (/cm²˜eV),whereas the interface state of the second sample including the CVD-SiO₂film shows an about an order of magnitude worse result. On the otherhand, it is ascertained that the third sample including the HfO₂ filmhas a good interface of about 3E10/cm²·eV and is close to the thermaloxide film. Furthermore, it has been known that the above-describedindividual materials, which constitute the films having negative fixedcharges, other than HfO₂ have good interface states close to the thermaloxide film similarly to HfO₂.

Next, the film thickness Tox in terms of oxide film versus the flat bandvoltage Vfb was examined in the case where the film 25, which had apositive fixed charge, was formed. The results thereof are shown in FIG.24.

As shown in FIG. 24, in the case where the flat band voltage is largerthan that of the thermal oxide film, there is a negative voltage in thefilm, and the silicon (Si) surface forms holes. Examples of suchlaminated films include a film in which a HfO₂ film and a CVD-SiO₂ filmare laminated on a silicon (Si) substrate surface sequentially from alower layer. On the other hand, in the case where the flat band voltageis smaller than that of the thermal oxide film, there is a positivevoltage in the film, and the silicon (Si) surface forms electrons(electrons). Examples of such laminated films include a film in which aCVD-SiO₂ film, a CVD-SiN film, a HfO₂ film, and a CVD-SiO₂ film arelaminated on a silicon (Si) substrate surface sequentially from a lowerlayer. Here, if the film thickness of the CVD-SiN film is increased, theflat band voltage shifts in the negative direction significantly ascompared with that of the thermal oxide film. Furthermore, an influenceof the positive charge in the CVD-SiN film cancels the negative chargeof hafnium oxide (HfO₂).

Regarding the solid-state imaging device 1 to the solid-state imagingdevice 5 in the above-described individual examples, as described above,in the case where nitrogen (N) is contained in the film 22, which has anegative fixed charge, after the film 22, which has a negative fixedcharge, is formed, nitrogen (N) can be contained by a nitridingtreatment with high-frequency plasma or microwave plasma. Moreover, theabove-described film 22, which has a negative fixed charge, is subjectedto an electron beam curing treatment through electron beam irradiationafter film formation and, thereby, the negative fixed charge in the filmcan be increased.

Next, an embodiment (first example) of a solid-state imaging device(second solid-state imaging device) according to the present inventionwill be described with reference to a key portion configurationsectional view shown in FIG. 25. In this regard, in FIG. 25, alight-shield film to shield a part of the light-receiving portion andthe peripheral circuit portion from light, a color filter layer todisperse the light incident on the light-receiving portion, a condenserlens to condense the incident light on the light-receiving portion, andthe like are not shown in the drawing.

As shown in FIG. 25, the solid-state imaging device 6 includes thelight-receiving portions 12, which photoelectrically convert incidentlight, on the semiconductor substrate (or semiconductor layer) 11 andincludes the peripheral circuit portion 14, in which a peripheralcircuit (for example, a circuit 14C) is disposed on the portion besidethe light-receiving portion 12 with the pixel isolation region 13therebetween. An insulating film 27 is disposed on the light-receivingsurface 12 s of the above-described light-receiving portion (including ahole accumulation layer 23 described later) 12. This insulating film 27is formed from, for example, a silicon oxide (SiO₂) film. A film 28,which applies a negative voltage, is disposed on the above-describedinsulating film 27.

In the drawing, the above-described insulating film 27 is disposedhaving a thickness above the peripheral circuit portion 14 larger thanthe thickness above the above-described light-receiving portion 12 insuch a way that the distance of the above-described film 28, whichapplies a negative voltage, from the surface of the above-describedperipheral circuit portion 14 becomes larger than the distance from thesurface of the above-described light-receiving portion 12. Furthermore,in the case where the above-described insulating film 27 is formed from,for example, a silicon oxide film, this insulating film 27 has afunction similar to that of the above-described film 21, which lowers ainterface state, on the light-receiving portion 12. For that purpose, itis preferable that the above-described insulating film 27 on theabove-described light-receiving portion 12 is disposed having a filmthickness of, for example, 1 atomic layer or more, and 100 nm or less.Consequently, when a negative voltage is applied to the film 28, whichapplies a negative voltage, the hole accumulation layer 23 is formed onthe light-receiving surface side of the above-described light-receivingportion 12.

In the case where the above-described solid-state imaging device 6 is aCMOS image sensor, examples of peripheral circuits of theabove-described peripheral circuit portion 14 include pixel circuitscomposed of transistors, e.g., a transfer transistor, a resettransistor, an amplifying transistor, and a selection transistor.Furthermore, a drive circuit to effect an operation to read signals oflines to be read in a pixel array portion composed of a plurality oflight-receiving portions 12, a vertical scanning circuit to transfer thesignals read, a shift register or an address decoder, a horizontalscanning circuit, and the like are included.

Alternatively, in the case where the above-described solid-state imagingdevice 6 is a CCD image sensor, examples of peripheral circuits of theabove-described peripheral circuit portion 14 include a read gate, whichreads photoelectrically converted signal charges from thelight-receiving portion to a vertical transfer gate, and a verticalcharge transfer portion, which transfers read signal charges in thevertical direction. Furthermore, a horizontal charge transfer portionand the like are included.

The above-described film 28, which applies a negative voltage, is formedfrom, for example, a film, which is transparent with respect to theincident light and which has electrical conductivity, and is formedfrom, for example, an electrically conductive film transparent withrespect to the visible light. As for such a film, an indium tin oxidefilm, an indium zinc oxide film, or an indium oxide film, a tin oxidefilm, a gallium zinc oxide film, or the like can be used.

Regarding the configuration on the film 28, which applies a negativevoltage, in the above-described solid-state imaging device 6, thelight-shield film to shield a part of the light-receiving portion 12 andthe peripheral circuit portion 14 from light, the color filter layer todisperse the light incident on at least the light-receiving portion 12,the condenser lens to condense the incident light on the light-receivingportion 12, and the like are disposed. As an example of theconfiguration, any one of the configurations of the above-describedsolid-state imaging devices 1, 2, and 3 can also be applied.

In the above-described solid-state imaging device (second solid-stateimaging device) 6, since the film 28, which applies a negative voltage,is disposed on the insulating film 27 disposed on the light-receivingsurface 12 s of the light-receiving portion 12, the hole accumulation(hole accumulation) layer is formed adequately at the interface on thelight-receiving surface 12 s side of the light-receiving portion 12 byan electric field generated through application of a negative voltage tothe film 28, which applies a negative voltage. Therefore, generation ofelectric charges (electrons) from the interface is suppressed and, inaddition, even when electric charges (electrons) are generated from theinterface, the electric charges do not flow into a charge storageportion serving as a potential well in the light-receiving portion, flowthrough the hole accumulation layer 23, in which many holes are present,and can be extinguished. Consequently, it can be prevented that theelectric charges resulting from the interface serve as a dark currentand are detected by the light-receiving portion 12, and a dark currentresulting from the interface state can be suppressed. Moreover, sincethe insulating film 27 serving as a film, which lowers the interfacestate, is disposed on the light-receiving surface 12 s of thelight-receiving portion 12, generation of electrons resulting from theinterface state is further suppressed, so that flowing of electrons,which serve as a dark current and which result from the interface state,into the light-receiving portion 12 is suppressed.

In addition, as shown in the drawing, the distance of theabove-described film 28, which applies a negative voltage, from thesurface of the above-described peripheral circuit portion 14 is made tobe larger than the distance from the surface of the above-describedlight-receiving portion 12 by the insulating film 27. Therefore, theinfluence exerted on the peripheral circuit portion 14 by the electricfield generated when a negative charge is applied to the film 28, whichapplies a negative voltage, is reduced. Consequently, a malfunction ofthe circuit in the peripheral circuit portion 14 can be eliminated.

Next, an embodiment (second example) of the solid-state imaging device(second solid-state imaging device) will be described with reference toa key portion configuration sectional view shown in FIG. 26. In thisregard, in FIG. 26, a light-shield film to shield a part of thelight-receiving portion and the peripheral circuit portion from light, acolor filter layer to disperse the light incident on the light-receivingportion, a condenser lens to condense the incident light on thelight-receiving portion, and the like are not shown in the drawing.

As shown in FIG. 26, in the solid-state imaging device 7, a film 25 tokeep the film, which applies a negative voltage, away from the surfaceof the light-receiving surface is disposed on the above-describedperipheral circuit portion 14, in actuality, between the insulating film27 and the above-described film 28, which applies a negative voltage, inthe above-described solid-state imaging device 6. It is desirable thatthe above-described film 25 has a positive fixed charge to cancel theinfluence of the negative voltage. It is enough that the film 25, whichhas a positive fixed charge, is disposed above the above-describedperipheral circuit portion 14 and under the above-described film 28,which applies a negative voltage, and it does not a matter whether onthe above-described insulating film 27 or under the insulating film 27.Furthermore, the drawing shows the case where the insulating film 27 isformed from a film having a uniform thickness. However, the insulatingfilm may have a thickness above the peripheral circuit portion 14 largerthan the thickness above the light-receiving portion 12, as in theabove-described solid-state imaging device 6.

An examples of the above-described film 25, which has a positive fixedcharge, is a silicon nitride film.

As described above, since the film 25, which has a positive fixedcharge, is disposed between the above-described peripheral circuitportion 14 and the above-described film 28, which applies a negativevoltage, the negative electric field generated when a negative charge isapplied to the film 28, which applies a negative voltage, is reduced bya positive fixed charge in the film 25, which has the positive fixedcharge. Therefore, the influence due to this negative electric field isnot exerted on the peripheral circuit portion 14. Consequently, amalfunction of the peripheral circuit portion 14 due to the negativeelectric field can be prevented and the reliability of the peripheralcircuit portion 14 is enhanced. The above-described configuration inwhich the film 25, which has a positive fixed charge, is disposed abovethe above-described peripheral circuit portion 14 and under theabove-described film 28, which applies a negative voltage, can also beapplied to the above-described solid-state imaging device 6, and theeffects similar to those of the solid-state imaging device 7 can beobtained.

Next, an embodiment (first example) of the method for manufacturing asolid-state imaging device (second manufacturing method) according tothe present invention will be described with reference to productionstep sectional views of a key portion shown in FIG. 27 to FIG. 29. InFIG. 27 to FIG. 29, production steps of the above-described solid-stateimaging device 4 are shown as an example.

As shown in FIG. 27 (1), the light-receiving portions 12, whichphotoelectrically convert incident light, the pixel isolation regions13, which isolate the light-receiving portions 12, the peripheralcircuit portion 14, in which a peripheral circuit (for example, acircuit 14C) is disposed opposing to the light-receiving portion 12 withthe pixel isolation region 13 therebetween, and the like are formed onthe semiconductor substrate (or semiconductor layer) 11. As for thismanufacturing method, a manufacturing method in the public domain isused. Subsequently, an insulating film 29, which has alight-transmitting property with respect to the above-described incidentlight, is formed. This insulating film 29 is formed from, for example, asilicon oxide film.

Then, as shown in FIG. 27 (2), a resist mask 53 is formed on theabove-described insulating film 29 above the above-described peripheralcircuit portion 14 through resist application and the lithographytechnology.

Thereafter, as shown in FIG. 28 (3), the above-described insulating film29 is worked through etching by using the above-described resist mask 53(refer to FIG. 27 (2) described above), so that the insulating film 29is left on the above-described peripheral circuit portion 14.Subsequently, the above-described resist mask 53 is removed.

Next, as shown in FIG. 28 (4), the film 21, which covers theabove-described insulating film 29 and which lowers an interface state,is formed on the light-receiving surface 12 s of the above-describedlight-receiving portion 12, in actuality, on the above-describedsemiconductor substrate 11. This film 21, which lowers an interfacestate, is formed from, for example, a silicon oxide (SiO₂) film. In thismanner, the insulating film 27 is formed from the above-describedinsulating film 29 and the above-described film 21, which lowers aninterface state.

Then, as shown in FIG. 29 (5), the film 28, which applies a negativevoltage, is formed on the above-described film 21, which lowers aninterface state. The hole accumulation layer 23 is formed on thelight-receiving surface side of the above-described light-receivingportion 12 by applying a negative voltage to this film 28, which appliesa negative voltage. Therefore, at least on the light-receiving portion12, it is necessary that the above-described film 21, which lowers aninterface state, is formed having a film thickness to allow the holeaccumulation layer 23 to be formed on the light-receiving surface 12 sside of the above-described light-receiving portion 12 by the negativevoltage applied to the above-described film 28, which applies a negativevoltage. The film thickness thereof is specified to be, for example, 1atomic layer or more, and 100 nm or less.

The above-described film 28, which applies a negative voltage, is formedfrom, for example, a film which is transparent with respect to theincident light and which has electrical conductivity, and is formedfrom, for example, an electrically conductive film transparent withrespect to the visible light. As for such a film, an indium tin oxidefilm, an indium zinc oxide film, or an indium oxide film, a tin oxidefilm, a gallium zinc oxide film, or the like can be used.

In the above-described solid-state imaging device 6, the light-shieldfilm to shield a part of the light-receiving portion 12 and theperipheral circuit portion 14 from light, the color filter layer todisperse the light incident on at least the light-receiving portion 12,the condenser lens to condense the incident light on the light-receivingportion 12, and the like are disposed on the film 28, which applies anegative voltage. As for a manufacturing method therefor, as an example,any one of the methods described in the individual examples of theabove-described method for manufacturing a solid-state imaging device(first manufacturing method) can also be applied. In the first exampleof the method for manufacturing the above-described solid-state imagingdevice 6 (second manufacturing method), since the film 28, which appliesa negative voltage, is formed on the insulating film 27 disposed on thelight-receiving surface 12 s of the light-receiving portion 12, the holeaccumulation (hole accumulation) layer is formed adequately at theinterface on the light-receiving surface 12 s side of thelight-receiving portion 12 by an electric field generated throughapplication of a negative voltage to the film 28, which applies anegative voltage. Therefore, generation of electric charges (electrons)from the interface is suppressed and, in addition, even when electriccharges (electrons) are generated, the electric charges do not flow intoa charge storage portion serving as a potential well in thelight-receiving portion, flow through the hole accumulation layer 23, inwhich many holes are present, and can be extinguished. Consequently, itcan be prevented that the electric charges resulting from the interfaceserve as a dark current and are detected by the light-receiving portion12, and a dark current resulting from the interface state can besuppressed. Moreover, since the film 21, which lowers the interfacestate, is disposed on the light-receiving surface 12 s of thelight-receiving portion 12, generation of electrons resulting from theinterface state is further suppressed, so that flowing of electrons,which serve as a dark current, resulting from the interface state intothe light-receiving portion 12 is suppressed.

In addition, as shown in the drawing, the insulating film 27 is disposedhaving a thickness above the peripheral circuit portion 14 larger thanthe thickness of the insulating film 27 above the above-describedlight-receiving portion 12 in such a way that the distance of theabove-described film 28, which applies a negative voltage, from thesurface of the above-described peripheral circuit portion 14 becomeslarger than the distance from the surface of the above-describedlight-receiving portion 12 by the insulating film 27. Therefore, theinfluence exerted by the electric field generated when a negative chargeis applied to the film 28, which applies a negative voltage, on theperipheral circuit portion 14 is reduced. That is, the field strength isreduced, accumulation of holes on the surface of the peripheral circuitportion 14 is suppressed and, thereby, a malfunction of the circuit inthe peripheral circuit portion 14 can be eliminated.

Next, an embodiment (second example) of the method for manufacturing asolid-state imaging device (second manufacturing method) according tothe present invention will be described with reference to productionstep sectional views of a key portion shown in FIG. 30 and FIG. 31. InFIG. 30 and FIG. 31, production steps of the above-described solid-stateimaging device 4 are shown as an example.

As shown in FIG. 30 (1), the light-receiving portions 12, whichphotoelectrically convert incident light, the pixel isolation regions13, which isolate the light-receiving portions 12, the peripheralcircuit portion 14, in which a peripheral circuit (for example, acircuit 14C) is disposed opposing to the light-receiving portion 12 withthe pixel isolation region 13 therebetween, and the like are formed onthe semiconductor substrate (or semiconductor layer) 11. As for thismanufacturing method, a manufacturing method in the public domain isused. Subsequently, an insulating film 27, which has alight-transmitting property with respect to the above-described incidentlight, is formed. This insulating film 27 is formed from, for example, asilicon oxide film. Furthermore, the film 25, which has a positive fixedcharge, is formed on the above-described insulating film 27. This film25, which has a positive fixed charge, is formed from, for example, asilicon nitride film.

Then, as shown in FIG. 30 (2), a resist mask 54 is formed on theabove-described film 25, which has a positive fixed charge, above theabove-described peripheral circuit portion 14 through resist applicationand the lithography technology.

Thereafter, as shown in FIG. 31 (3), the above-described film 25, whichhas a positive fixed charge, is worked through etching by using theabove-described resist mask 54 (refer to FIG. 30 (2) described above),so that the film 25, which has a positive fixed charge, is left on theabove-described peripheral circuit portion 14. Subsequently, theabove-described resist mask 54 is removed.

Next, as shown in FIG. 31 (4), the film 28, which applies a negativevoltage, is formed on the above-described insulating film 27 and theabove-described film 25, which has a positive fixed charge. The holeaccumulation layer 23 is formed on the light-receiving surface side ofthe above-described light-receiving portion 12 through application of anegative voltage to this film 28, which applies a negative voltage. Atthat time, the above-described insulating film 27 is allowed to functionas a film, which lowers an interface state. For that purpose, at leaston the light-receiving portion 12, it is necessary that theabove-described insulating film 27 is formed having a film thickness toallow the hole accumulation layer 23 to be formed on the light-receivingsurface 12 s side of the above-described light-receiving portion 12 bythe negative voltage applied to the above-described film 28, whichapplies a negative voltage. The film thickness thereof is specified tobe, for example, 1 atomic layer or more, and 100 nm or less.

The above-described film 28, which applies a negative voltage, is formedfrom, for example, a film which is transparent with respect to theincident light and which has electrical conductivity, and is formedfrom, for example, an electrically conductive film transparent withrespect to the visible light. As for such a film, an indium tin oxidefilm, an indium zinc oxide film, or an indium oxide film, a tin oxidefilm, a gallium zinc oxide film, or the like can be used.

In the above-described solid-state imaging device 7, although not shownin the drawing, the light-shield film to shield a part of thelight-receiving portion 12 and the peripheral circuit portion 14 fromlight, the color filter layer to disperse the light incident on at leastthe light-receiving portion 12, the condenser lens to condense theincident light on the light-receiving portion 12, and the like aredisposed on the film 28 which applies a negative voltage. As for amanufacturing method therefor, as an example, any one of the methodsdescribed in the individual examples of the above-described method formanufacturing a solid-state imaging device (first manufacturing method)can also be applied.

In the second example of the above-described method for manufacturingthe solid-state imaging device 7 (second manufacturing method), sincethe film 28, which applies a negative voltage, is formed on theinsulating film 27 disposed on the light-receiving surface 12 s of thelight-receiving portion 12, the hole accumulation (hole accumulation)layer is formed adequately at the interface on the light-receivingsurface 12 s side of the light-receiving portion 12 by an electric fieldgenerated through application of a negative voltage to the film 28,which applies a negative voltage. Therefore, generation of electriccharges (electrons) from the interface is suppressed and, in addition,even when electric charges (electrons) are generated from the interface,the electric charges do not flow into a charge storage portion servingas a potential well in the light-receiving portion, flow through thehole accumulation layer 23, in which many holes are present, and can beextinguished. Consequently, it can be prevented that the electriccharges resulting from the interface serve as a dark current and aredetected by the light-receiving portion 12, and a dark current resultingfrom the interface state can be suppressed. Moreover, since the film 21,which lowers the interface state, is disposed on the light-receivingsurface 12 s of the light-receiving portion 12, generation of electronsresulting from the interface state is further suppressed, so thatflowing of electrons, which serve as a dark current, resulting from theinterface state into the light-receiving portion 12 is suppressed.

In addition, since the film 25, which has a positive fixed charge, isdisposed between the above-described peripheral circuit portion 14 andthe above-described film 28, which applies a negative voltage, thenegative electric field generated when a negative charge is applied tothe film 28, which applies a negative voltage, is reduced by a positivefixed charge in the film 25 having the positive fixed charge. Therefore,the influence due to this negative electric field is not exerted on theperipheral circuit portion 14. Consequently, a malfunction of theperipheral circuit portion 14 due to the negative electric field can beprevented. The above-described configuration in which the film 25, whichhas a positive fixed charge, is disposed above the above-describedperipheral circuit portion 14 and under the above-described film 28,which applies a negative voltage, can also be applied to theabove-described solid-state imaging device 6, and the effects similar tothose of the solid-state imaging device 7 can be obtained.

Next, an embodiment (example) of a solid-state imaging device (thirdsolid-state imaging device) will be described with reference to a keyportion configuration sectional view shown in FIG. 32. In this regard,in FIG. 32, the light-receiving portion is shown mainly, and theperipheral circuit portion, a wiring layer, a light-shield film toshield a part of the light-receiving portion and the peripheral circuitportion from light, a color filter layer to disperse the light incidenton the light-receiving portion, a condenser lens to condense theincident light on the light-receiving portion, and the like are notshown in the drawing.

As shown in FIG. 32, a solid-state imaging device 8 includes thelight-receiving portion 12, which photoelectrically converts incidentlight, on the semiconductor substrate (or semiconductor layer) 11. Aninsulating film 31 is disposed on the light-receiving surface 12 s sideof this light-receiving portion 12. This insulating film 31 is formedfrom, for example, silicon oxide (SiO₂) film. A film (hereafter referredto as a hole accumulation auxiliary film) 32, which has a value of workfunction larger than that of the interface on the light-receivingsurface 12 s side of the above-described light-receiving portion 12 toconduct photoelectric conversion, is disposed on the above-describedinsulating film 31. The hole accumulation layer 23 is formed on thebasis of this difference in work function. This hole accumulationauxiliary film 32 is not necessarily electrically connected to otherelements nor wirings and, therefore, may be an insulating film or afilm, e.g., a metal film, having electrical conductivity.

Moreover, a wiring layer 73 composed of, for example, a plurality ofwirings 71 and an insulating film 72 is disposed on the side opposite tothe light incident side of the semiconductor substrate 11 provided withthe above-described light-receiving portion 12. In addition, the wiringlayer 73 is supported by a support substrate 74.

For example, since the hole accumulation layer 23 is formed from silicon(Si), the value of work function thereof is about 5.1 eV. Therefore, itis enough that the above-described hole accumulation auxiliary film 32has the value of work function larger than 5.1.

For example, in the case where a metal film is used, according toChronological Scientific Tables, the value of work function of aniridium (110) film is 5.42, the value of work function of an iridium(111) film is 5.76, the value of work function of a nickel film is 5.15,the value of work function of a palladium film is 5.55, the value ofwork function of an osmium film is 5.93, the value of work function of agold (100) film is 5.47, the value of work function of a gold (110) filmis 5.37, and the value of work function of a platinum film is 5.64.These films can be used as the above-described hole accumulationauxiliary film 32. Even films other than those described above can beused as the hole accumulation auxiliary film 32 insofar as the film is ametal film having a value of work function larger than that of theinterface on the light-receiving surface 12 s side of thelight-receiving portion 12. In this connection, the value of workfunction of ITO (In₂O₃) used as a transparent electrode is assumed to be4.8 eV. The work function of an oxide semiconductor can be controlled bya film formation method or impurity introduction.

The above-described hole accumulation auxiliary film 32 is disposed onthe light incident side and, therefore, it is important to be formedhaving a film thickness suitable for transmitting the incident light. Asfor the incident light transmittance thereof, it is preferable to haveas high transmittance as possible. For example, it is preferable thatthe transmittance of 95% or more is ensured.

Furthermore, it is enough that the hole accumulation auxiliary film 32can make use of the difference in work function from that of the surfaceof the light-receiving portion 12, and there is no lower limit for theresistance value. Therefore, even in the case where, for example, anelectrically conductive film is used, it is not necessary to form havinga large film thickness. For example, when the incident light intensityis assumed to be I₀ and the absorption coefficient is assumed to be α(where α=(4πk)/λ, k is a Boltzmann constant, and λ is a wavelength ofincident light), the light intensity at the position of depth z isrepresented by I(z)=I₀exp(−α·z). Consequently, the thickness atI(z)/I₀=0.8 is determined to be, for example 1.9 nm for the iridiumfilm, 4.8 nm for the gold film, and 3.4 nm for the platinum film,although different depending on the type of film. However, it is clearthat 2 nm or less is preferable.

Moreover, the above-described hole accumulation auxiliary film 32 may bean organic film. For example, polyethylenedioxythiophene(polyethylenedioxythiophene) can also be used. As described above, theabove-described hole accumulation auxiliary film 32 may be anelectrically conductive film, an insulating film, or a semiconductorfilm insofar as the film has the value of work function higher than thevalue of work function of the interface on the light-receiving surface12 s side of the light-receiving portion 12.

The above-described solid-state imaging device 8 includes the film (holeaccumulation auxiliary film) 32, which has a value of work functionlarger than that of the interface on the light-receiving surface 12 sside of the above-described light-receiving portion 12 on the insulatingfilm 31 disposed on the light-receiving portion 12 and, thereby, thehole accumulation efficiency of the hole accumulation layer 23 isincreased, so that the hole accumulation layer 23 disposed at thelight-receiving side interface of the light-receiving portion 12 canaccumulate adequate holes. Consequently, a dark current is reduced.

Next, an example of the configuration of a solid-state imaging deviceincluding the hole accumulation auxiliary film 32 will be described withreference to FIG. 33. FIG. 33 shows a CMOS image sensor.

As shown in FIG. 33, a plurality of pixel portions 61 including thelight-receiving portion (for example, photodiode) 12 which converts theincident light to an electric signal, a transistor group 55 composed oftransfer transistors, amplifying transistors, reset transistors, etc.,(a part of them are shown in the drawing), and the like are disposed onthe semiconductor substrate 11. As for the above-described semiconductorsubstrate 11, for example, a silicon substrate is used. Furthermore, asignal processing portion (not shown in the drawing) to process thesignal charges read from the individual light-receiving portions 12 isdisposed.

The element isolation regions 13 are disposed in a part of thecircumference of the above-described pixel portion 61, for example,between the pixel portions 61 in the longitudinal direction or thetransverse direction.

In addition, the wiring layer 73 is disposed on the surface side of thesemiconductor substrate 11 (in the drawing, under the semiconductorsubstrate 11) provided with the above-described light-receiving portions12. This wiring layer 73 is composed of the wirings 71 and theinsulating film 72 covering the wirings 71. The above-described wiringlayer 73 is provided with the support substrate 74. This supportsubstrate 74 is formed from, for example, a silicon substrate.

Furthermore, in the above-described solid-state imaging device 8, thehole accumulation layer 23 is disposed on the back surface side of thesemiconductor substrate 11, and the above-described hole accumulationauxiliary film 32 is disposed on the upper surface thereof with theinsulating film 31 therebetween. Moreover, an organic color filter 44 isdisposed thereon with an insulating film (not shown in the drawing)therebetween. This color filter 44 is disposed in accordance with theabove-described light-receiving portion 12 and is formed by, forexample, arranging blue (Blue), red (Red), and green (Green) organiccolor filters in a checkered pattern, for example. In addition, acondenser lens 45 to condense incident light on each light-receivingportion 12 is disposed on each organic color filter 44.

Next, an embodiment (first example) of the method for manufacturing asolid-state imaging device (third manufacturing method) according to thepresent invention will be described with reference to a flow chart shownin FIG. 34, production step sectional views shown in FIG. 35, andproduction step sectional views of a key portion shown in FIG. 36. InFIG. 34 to FIG. 36, production steps of the above-described solid-stateimaging device 8 are shown as an example.

As shown in FIG. 34 (1) and FIG. 35 (1), initially, an SOI substrate 81,in which a silicon layer 84 is disposed on a silicon substrate 82 withan insulating layer (for example, silicon oxide layer) 83 therebetween,is prepared, and a back surface mark 85 for alignment is formed in thesilicon layer 84.

Subsequently, as shown in FIG. 34 (2) and FIG. 35 (2), formation of anelement isolation region (not shown in the drawing), formation of thehole accumulation layer 23, formation of the light-receiving portion 12,formation of the transistor group 55, formation of the wiring layer 73,and the like are conducted on the silicon layer 84 of the SOI substrate81. Among them, the hole accumulation layer 23 may be formed in a stepafter substrate thickness reduction in the downstream.

Then, as shown in FIG. 34 (3) and FIG. 35 (3), the wiring layer 73 andthe support substrate 74 are bonded together.

Thereafter, as shown in FIG. 34 (4) and FIG. 35 (4), thickness reductionof the SOI substrate 81 is conducted. Here, the silicon substrate 82 isremoved through, for example, grinding and polishing.

Although not shown in the drawing, the above-described hole accumulationlayer 23 may be formed by forming a cap film (not shown in the drawing)after removal of the insulating layer 83 from the SOI substrate 81 andconducting impurity introduction and an activation treatment. As anexample, a plasma-TEOS silicon oxide film having a thickness of 30 nm isformed as the cap film and the impurity introduction is conductedthrough ion implantation of boron. As for the ion implantationcondition, for example, implantation energy is set at 20 keV, and theamount of dose is set at 1×10¹³/cm². In this connection, it ispreferable that activation is conducted through annealing at 400° C. orlower in such a way that bonding between the wiring layer 73 and thesupport substrate 74 is not broken. Subsequently, the above-describedcap layer is removed through, for example, a dilute hydrofluoric acidtreatment. At this time, the insulating layer 83 may be removed from theSOI substrate 81.

In this manner, as shown in FIG. 36 (1), the hole accumulation layer 23is formed on the light-receiving portion 12.

Next, as shown in FIG. 36 (2), the insulating film 31 is formed on thehole accumulation layer 23 (light incident side). As an example, aplasma-TEOS silicon oxide film having a thickness of 30 nm is formed.

Then, as shown in FIG. 36 (3), the hole accumulation auxiliary film 32,which is a film having a value of work function larger than that of theinterface (the value of work function is about 5.1 eV) on thelight-receiving surface 12 s side of the above-described light-receivingportion 12, is formed on the above-described insulating film 31 (lightincident side). As an example, a platinum (Pt) film, which is a metalthin film and which has a value of work function of 5.6 eV, is formedhaving a thickness of 3 nm through sputtering. Examples of candidatesfor other metal thin films include iridium (Ir), rhenium (Re), nickel(Ni), palladium (Pd), cobalt (Co), ruthenium (Ru), rhodium (Rh), osmium(Os), and gold (Au). Alloys can be employed, as a matter of course.

In this connection, as for the material for the above-described holeaccumulation auxiliary film 32 in this example, even ITO (In₂O₃) canalso be employed because the value of work function of the interface onthe light-receiving surface side of the light-receiving portion is about5.1 eV. ITO can have a value of work function of 4.5 eV to 5.6 eVdepending on the film formation process. Furthermore, as for other oxidesemiconductors, since semiconductors, in which RuO₂, SnO₂, IrO₂, OsO₂,ZnO, ReO₂, MoO₂, and acceptor impurities are introduced,polyethylenedioxythiophene (polyethylenedioxythiophene: PEDOT), which isan organic material, and the like are allowed to have values of workfunction larger than 5.1 eV, they can serve as materials for the holeaccumulation auxiliary film 32. Moreover, examples of film formationtechniques include ALD, CVD, and vapor phase doping as film formationtechniques at 400° C. or lower.

Subsequently, as shown in FIG. 34 (5) and FIG. 35 (5), a back surfaceelectrode 92 is formed through the medium of barrier metal 91.

Then, as shown in FIG. 34 (6) and FIG. 35 (6), the color filter layer 44is formed above the light-receiving portion 12 and, thereafter, thecondenser lens 45 is formed. In this manner, the solid-state imagingdevice 8 is formed.

In the above-described method for manufacturing a solid-state imagingdevice (third manufacturing method), since the hole accumulationauxiliary film 32, which is a film having a value of work functionlarger than that of the interface on the light-receiving surface 12 sside of the above-described light-receiving portion 12, is formed on theinsulating film 31 disposed on the light-receiving portion 12, the holeaccumulation efficiency of the hole accumulation layer 23 is increased,so that the hole accumulation layer 23 disposed at the light-receivingsurface 12 s side interface of the light-receiving portion 12 canaccumulate adequate holes. Consequently, a dark current is reduced. Inthis connection, it is enough that the above-described hole accumulationauxiliary film 32 has the value of work function higher than the valueof work function of the hole accumulation layer 23 and it is notnecessary to pass a current. Therefore, an electrically conductive film,an insulating film, or a semiconductor film may be employed. Hence, amaterial exhibiting high resistance can be selected for the holeaccumulation auxiliary film 32. In addition, there is a feature that anexternal signal input terminal is unnecessary for the hole accumulationauxiliary film 32.

The solid-state imaging devices 1 to 8 of the above-described individualexamples are provided with a plurality of pixel portions including thelight-receiving portions to convert the amounts of incident light toelectric signals and wiring layers on one surface side of thesemiconductor substrates including the individual pixel portions, andcan be applied to a back-side illumination solid-state imaging devicehaving a configuration in which the light incident from the sideopposite to the surface provided with the wiring layer is received withthe above-described individual light-receiving portions. As a matter ofcourse, it is possible to apply to a surface illumination solid-stateimaging device, wherein a wiring layer is disposed on thelight-receiving surface side and an optical path of the incident lightincident on the light-receiving portion is specified to be a region, inwhich the above-described wiring layer is not disposed, in order thatthe incident light incident on the light-receiving portion is notinterfered.

Next, an embodiment (example) according to an imaging apparatus of thepresent invention will be described with reference to a block diagramshown in FIG. 37. Examples of this imaging apparatuses include videocameras, digital steel cameras, and cameras of cellular phones.

As shown in FIG. 37, an imaging apparatus 500 is provided with asolid-state imaging device (not shown in the drawing) in an imagingportion 501. An image-focusing optical portion 502 to form an image isprovided on the light-condensing side of the imaging portion 501.Furthermore, the imaging portion 501 is connected to a drive circuit todrive it and a signal processing portion 503 including, for example, asignal processing circuit to process a signal, which isphotoelectrically converted with the solid-state imaging device, to animage. Moreover, an image signal processed with the above-describedsignal processing portion can be stored in an image storage portion (notshown in the drawing). In the above-described imaging apparatus 500, thesolid-state imaging device 1 to the solid-state imaging device 8explained in the above-described embodiments can be used for theabove-described solid-state imaging device.

The solid-state imaging device 1 or the solid-state imaging device 2according to the present invention or the solid-state imaging devicehaving the configuration shown in FIG. 4, described above, in which thereflection film is disposed and the condenser lens is included, is usedfor the imaging apparatus 500 according to the present invention.Therefore, in a manner similar to that described above, since thesolid-state imaging device capable of enhancing the colorreproducibility and the resolution is used, there is an advantage that ahigh-quality image can be recorded.

Incidentally, the imaging apparatus 500 according to the presentinvention is not limited to the above-described configuration, but canbe applied to an imaging apparatus having any configuration includingthe solid-state imaging device.

The above-described solid-state imaging device 1 to the solid-stateimaging device 8 and the like may be made in the form of one chip or inthe form of a module, in which an imaging portion and a signalprocessing portion or an optical system are integrally packaged andwhich has an imaging function. In addition, the present invention can beapplied to not only solid-state imaging devices, but also imagingapparatuses. In this case, as for the imaging apparatus, an effect ofimproving image quality is obtained. Here, the imaging apparatus refersto, for example, a portable apparatus having a camera or an imagingfunction. In this regard, “imaging” includes not only picking up ofimage in usual photo shooting with a camera, but also fingerprintdetection and the like in a broad sense.

1-6. (canceled)
 7. A solid-state imaging device, comprising: alight-receiving portion to photoelectrically convert incident light,including: an insulating film which is disposed on a light-receivingsurface of the light-receiving portion and which transmits the incidentlight; and a film which is disposed on the insulating film and whichapplies a negative voltage, wherein a hole accumulation layer isdisposed on the light-receiving surface side of the light-receivingportion.
 8. The solid-state imaging device of claim 7, wherein the film,which applies a negative voltage, is formed from an electricallyconductive material which transmits the incident light.
 9. Thesolid-state imaging device of claim 7, further comprising: a peripheralcircuit portion, in which a peripheral circuit is disposed, in a portionbeside the light-receiving portion, wherein an insulating film isdisposed between a surface of the peripheral circuit portion and thefilm, which applies a negative voltage, in such a way that the distanceof the film, which applies a negative voltage, from the surface of theperipheral circuit portion is larger than the distance from a surface ofthe light-receiving portion.
 10. The solid-state imaging device of claim7, further comprising: a peripheral circuit portion, in which aperipheral circuit is disposed, in a portion beside the light-receivingportion, wherein a film formed from one type of silicon oxide film,silicon nitride film, and silicon oxynitride film or a laminatedstructure of a plurality of types of films is disposed above theperipheral circuit portion and under the film, which applies a negativevoltage.
 11. The solid-state imaging device of claim 7, wherein thesolid-state imaging device is a back-side illumination solid-stateimaging device comprising a plurality of pixel portions having alight-receiving portion, which converts the amount of incident light toan electric signal, and a wiring layer on one surface side of asemiconductor substrate provided with the pixel portions, wherein thelight incident from the side opposite to the surface provided with thewiring layer is received with the light-receiving portion.
 12. Asolid-state imaging device, comprising: a light-receiving portion tophotoelectrically convert incident light, including: an insulating filmwhich is disposed as an upper layer on a light-receiving surface side ofthe light-receiving portion; and a film which is disposed on theinsulating film and which has a value of work function larger than thatof an interface on the light-receiving surface side of thelight-receiving portion to conduct photoelectric conversion.
 13. Thesolid-state imaging device of claim 12, wherein the solid-state imagingdevice is a back-side illumination solid-state imaging device comprisinga plurality of pixel portions having a light-receiving portion, whichconverts the amount of incident light to an electric signal, and awiring layer on one surface side of a semiconductor substrate providedwith the pixel portions, wherein the light incident from the sideopposite to the surface provided with the wiring layer is received withthe light-receiving portion.
 14. (canceled)
 15. A method formanufacturing a solid-state imaging device having a light-receivingportion, which photoelectrically converts incident light and which isdisposed on a semiconductor substrate, comprising: forming an insulatingfilm, which transmits the incident light, on a light-receiving surfaceof the light-receiving portion; and forming a film, which applies anegative voltage, on the insulating film, wherein a hole accumulationlayer is formed on the light-receiving surface side of thelight-receiving portion by applying a negative voltage to the film,which applies a negative voltage.
 16. A method for manufacturing asolid-state imaging device having a light-receiving portion, whichphotoelectrically converts incident light and which is disposed on asemiconductor substrate, comprising: forming an insulating film as anupper layer on a light-receiving surface side of the light-receivingportion; and forming a film, which has a value of work function largerthan that of an interface on the light-receiving surface side of thelight-receiving portion to conduct photoelectric conversion, on theinsulating film.
 17. (canceled)
 18. An imaging apparatus, comprising: alight-condensing optical portion, which condenses incident light; asolid-state imaging device, which receives and photoelectricallyconverts the incident light condensed in the light-condensing opticalportion; and a signal processing portion, which processes aphotoelectrically converted signal charge, wherein the solid-stateimaging device includes: an insulating film, which is disposed on alight-receiving surface of a light-receiving portion of the solid-stateimaging device to photoelectrically convert the incident light, whereinthe insulating film is formed from an insulating film, which transmitsthe incident light; a film, which is disposed on the insulating film andwhich applies a negative voltage; and a hole accumulation layer isdisposed on the light-receiving surface of the light-receiving portion.19. An imaging apparatus, comprising: a light-condensing opticalportion, which condenses incident light; a solid-state imaging device,which receives and photoelectrically converts the incident lightcondensed in the light-condensing optical portion; and a signalprocessing portion, which processes a photoelectrically converted signalcharge, wherein the solid-state imaging device includes an insulatingfilm, which is disposed as an upper layer on a light-receiving surfaceside of a light-receiving portion of the solid-state imaging device tophotoelectrically convert the incident light to a signal charge; and afilm, which is disposed on the insulating film and which has a value ofwork function larger than that of the interface on the light-receivingsurface side of the light-receiving portion to conduct photoelectricconversion.